ldlinux.asm

   1 ; -*- fundamental -*- (asm-mode sucks)
   2 ; $Id$
   3 ; ****************************************************************************
   4 ;
   5 ;  ldlinux.asm
   6 ;
   7 ;  A program to boot Linux kernels off an MS-DOS formatted floppy disk.  This
   8 ;  functionality is good to have for installation floppies, where it may
   9 ;  be hard to find a functional Linux system to run LILO off.
  10 ;
  11 ;  This program allows manipulation of the disk to take place entirely
  12 ;  from MS-LOSS, and can be especially useful in conjunction with the
  13 ;  umsdos filesystem.
  14 ;
  15 ;   Copyright (C) 1994-2005  H. Peter Anvin
  16 ;
  17 ;  This program is free software; you can redistribute it and/or modify
  18 ;  it under the terms of the GNU General Public License as published by
  19 ;  the Free Software Foundation, Inc., 53 Temple Place Ste 330,
  20 ;  Boston MA 02111-1307, USA; either version 2 of the License, or
  21 ;  (at your option) any later version; incorporated herein by reference.
  22 ;
  23 ; ****************************************************************************
  24
  25 %ifndef IS_MDSLINUX
  26 %define IS_SYSLINUX 1
  27 %endif
  28 %include "macros.inc"
  29 %include "config.inc"
  30 %include "kernel.inc"
  31 %include "bios.inc"
  32 %include "tracers.inc"
  33 %include "layout.inc"
  34 ;
  35 ; Some semi-configurable constants... change on your own risk.
  36 ;
  37 my_id           equ syslinux_id
  38 FILENAME_MAX_LG2 equ 4                  ; log2(Max filename size Including final null)
  39 FILENAME_MAX    equ 11                  ; Max mangled filename size
  40 NULLFILE        equ ' '                 ; First char space == null filename
  41 NULLOFFSET      equ 0                   ; Position in which to look
  42 retry_count     equ 16                  ; How patient are we with the disk?
  43 %assign HIGHMEM_SLOP 0                  ; Avoid this much memory near the top
  44 LDLINUX_MAGIC   equ 0x3eb202fe          ; A random number to identify ourselves with
  45
  46 MAX_OPEN_LG2    equ 6                   ; log2(Max number of open files)
  47 MAX_OPEN        equ (1 << MAX_OPEN_LG2)
  48
  49 SECTOR_SHIFT    equ 9
  50 SECTOR_SIZE     equ (1 << SECTOR_SHIFT)
  51
  52 ;
  53 ; This is what we need to do when idle
  54 ;
  55 %macro  RESET_IDLE 0
  56         ; Nothing
  57 %endmacro
  58 %macro  DO_IDLE 0
  59         ; Nothing
  60 %endmacro
  61
  62 ;
  63 ; The following structure is used for "virtual kernels"; i.e. LILO-style
  64 ; option labels.  The options we permit here are `kernel' and `append
  65 ; Since there is no room in the bottom 64K for all of these, we
  66 ; stick them at vk_seg:0000 and copy them down before we need them.
  67 ;
  68                 struc vkernel
  69 vk_vname:       resb FILENAME_MAX       ; Virtual name **MUST BE FIRST!**
  70 vk_rname:       resb FILENAME_MAX       ; Real name
  71 vk_appendlen:   resw 1
  72                 alignb 4
  73 vk_append:      resb max_cmd_len+1      ; Command line
  74                 alignb 4
  75 vk_end:         equ $                   ; Should be <= vk_size
  76                 endstruc
  77
  78 ;
  79 ; Segment assignments in the bottom 640K
  80 ; Stick to the low 512K in case we're using something like M-systems flash
  81 ; which load a driver into low RAM (evil!!)
  82 ;
  83 ; 0000h - main code/data segment (and BIOS segment)
  84 ;
  85 real_mode_seg   equ 4000h
  86 cache_seg       equ 3000h               ; 64K area for metadata cache
  87 vk_seg          equ 2000h               ; Virtual kernels
  88 xfer_buf_seg    equ 1000h               ; Bounce buffer for I/O to high mem
  89 comboot_seg     equ real_mode_seg       ; COMBOOT image loading zone
  90
  91 ;
  92 ; File structure.  This holds the information for each currently open file.
  93 ;
  94                 struc open_file_t
  95 file_sector     resd 1                  ; Sector pointer (0 = structure free)
  96 file_left       resd 1                  ; Number of sectors left
  97                 endstruc
  98
  99 %ifndef DEPEND
 100 %if (open_file_t_size & (open_file_t_size-1))
 101 %error "open_file_t is not a power of 2"
 102 %endif
 103 %endif
 104
 105 ; ---------------------------------------------------------------------------
 106 ;   BEGIN CODE
 107 ; ---------------------------------------------------------------------------
 108
 109 ;
 110 ; Memory below this point is reserved for the BIOS and the MBR
 111 ;
 112                 section .earlybss
 113 trackbufsize    equ 8192
 114 trackbuf        resb trackbufsize       ; Track buffer goes here
 115 getcbuf         resb trackbufsize
 116                 ; ends at 4800h
 117
 118                 section .bss
 119                 alignb 8
 120
 121                 ; Expanded superblock
 122 SuperInfo       equ $
 123                 resq 16                 ; The first 16 bytes expanded 8 times
 124 FAT             resd 1                  ; Location of (first) FAT
 125 RootDirArea     resd 1                  ; Location of root directory area
 126 RootDir         resd 1                  ; Location of root directory proper
 127 DataArea        resd 1                  ; Location of data area
 128 RootDirSize     resd 1                  ; Root dir size in sectors
 129 TotalSectors    resd 1                  ; Total number of sectors
 130 EndSector       resd 1                  ; Location of filesystem end
 131 ClustSize       resd 1                  ; Bytes/cluster
 132 ClustMask       resd 1                  ; Sectors/cluster - 1
 133 CopySuper       resb 1                  ; Distinguish .bs versus .bss
 134 DriveNumber     resb 1                  ; BIOS drive number
 135 ClustShift      resb 1                  ; Shift count for sectors/cluster
 136 ClustByteShift  resb 1                  ; Shift count for bytes/cluster
 137
 138                 alignb open_file_t_size
 139 Files           resb MAX_OPEN*open_file_t_size
 140
 141 ;
 142 ; Constants for the xfer_buf_seg
 143 ;
 144 ; The xfer_buf_seg is also used to store message file buffers.  We
 145 ; need two trackbuffers (text and graphics), plus a work buffer
 146 ; for the graphics decompressor.
 147 ;
 148 xbs_textbuf     equ 0                   ; Also hard-coded, do not change
 149 xbs_vgabuf      equ trackbufsize
 150 xbs_vgatmpbuf   equ 2*trackbufsize
 151
 152
 153                 section .text
 154 ;
 155 ; Some of the things that have to be saved very early are saved
 156 ; "close" to the initial stack pointer offset, in order to
 157 ; reduce the code size...
 158 ;
 159 StackBuf        equ $-44-32             ; Start the stack here (grow down - 4K)
 160 PartInfo        equ StackBuf            ; Saved partition table entry
 161 FloppyTable     equ PartInfo+16         ; Floppy info table (must follow PartInfo)
 162 OrigFDCTabPtr   equ StackBuf-4          ; The high dword on the stack
 163
 164 ;
 165 ; Primary entry point.  Tempting as though it may be, we can't put the
 166 ; initial "cli" here; the jmp opcode in the first byte is part of the
 167 ; "magic number" (using the term very loosely) for the DOS superblock.
 168 ;
 169 bootsec         equ $
 170                 jmp short start         ; 2 bytes
 171                 nop                     ; 1 byte
 172 ;
 173 ; "Superblock" follows -- it's in the boot sector, so it's already
 174 ; loaded and ready for us
 175 ;
 176 bsOemName       db 'SYSLINUX'           ; The SYS command sets this, so...
 177 ;
 178 ; These are the fields we actually care about.  We end up expanding them
 179 ; all to dword size early in the code, so generate labels for both
 180 ; the expanded and unexpanded versions.
 181 ;
 182 %macro          superb 1
 183 bx %+ %1        equ SuperInfo+($-superblock)*8+4
 184 bs %+ %1        equ $
 185                 zb 1
 186 %endmacro
 187 %macro          superw 1
 188 bx %+ %1        equ SuperInfo+($-superblock)*8
 189 bs %+ %1        equ $
 190                 zw 1
 191 %endmacro
 192 %macro          superd 1
 193 bx %+ %1        equ $                   ; no expansion for dwords
 194 bs %+ %1        equ $
 195                 zd 1
 196 %endmacro
 197 superblock      equ $
 198                 superw BytesPerSec
 199                 superb SecPerClust
 200                 superw ResSectors
 201                 superb FATs
 202                 superw RootDirEnts
 203                 superw Sectors
 204                 superb Media
 205                 superw FATsecs
 206                 superw SecPerTrack
 207                 superw Heads
 208 superinfo_size  equ ($-superblock)-1    ; How much to expand
 209                 superd Hidden
 210                 superd HugeSectors
 211                 ;
 212                 ; This is as far as FAT12/16 and FAT32 are consistent
 213                 ;
 214                 zb 54                   ; FAT12/16 need 26 more bytes,
 215                                         ; FAT32 need 54 more bytes
 216 superblock_len  equ $-superblock
 217
 218 SecPerClust     equ bxSecPerClust
 219 ;
 220 ; Note we don't check the constraints above now; we did that at install
 221 ; time (we hope!)
 222 ;
 223 start:
 224                 cli                     ; No interrupts yet, please
 225                 cld                     ; Copy upwards
 226 ;
 227 ; Set up the stack
 228 ;
 229                 xor ax,ax
 230                 mov ss,ax
 231                 mov sp,StackBuf         ; Just below BSS
 232                 mov es,ax
 233 ;
 234 ; DS:SI may contain a partition table entry.  Preserve it for us.
 235 ;
 236                 mov cx,8                ; Save partition info
 237                 mov di,sp
 238                 rep movsw
 239
 240                 mov ds,ax               ; Now we can initialize DS...
 241
 242 ;
 243 ; Now sautee the BIOS floppy info block to that it will support decent-
 244 ; size transfers; the floppy block is 11 bytes and is stored in the
 245 ; INT 1Eh vector (brilliant waste of resources, eh?)
 246 ;
 247 ; Of course, if BIOSes had been properly programmed, we wouldn't have
 248 ; had to waste precious space with this code.
 249 ;
 250                 mov bx,fdctab
 251                 lfs si,[bx]             ; FS:SI -> original fdctab
 252                 push fs                 ; Save on stack in case we need to bail
 253                 push si
 254
 255                 ; Save the old fdctab even if hard disk so the stack layout
 256                 ; is the same.  The instructions above do not change the flags
 257                 mov [DriveNumber],dl    ; Save drive number in DL
 258                 and dl,dl               ; If floppy disk (00-7F), assume no
 259                                         ; partition table
 260                 js harddisk
 261
 262 floppy:
 263                 mov cl,6                ; 12 bytes (CX == 0)
 264                 ; es:di -> FloppyTable already
 265                 ; This should be safe to do now, interrupts are off...
 266                 mov [bx],di             ; FloppyTable
 267                 mov [bx+2],ax           ; Segment 0
 268                 fs rep movsw            ; Faster to move words
 269                 mov cl,[bsSecPerTrack]  ; Patch the sector count
 270                 mov [di-8],cl
 271                 ; AX == 0 here
 272                 int 13h                 ; Some BIOSes need this
 273
 274                 jmp short not_harddisk
 275 ;
 276 ; The drive number and possibly partition information was passed to us
 277 ; by the BIOS or previous boot loader (MBR).  Current "best practice" is to
 278 ; trust that rather than what the superblock contains.
 279 ;
 280 ; Would it be better to zero out bsHidden if we don't have a partition table?
 281 ;
 282 ; Note: di points to beyond the end of PartInfo
 283 ;
 284 harddisk:
 285                 test byte [di-16],7Fh   ; Sanity check: "active flag" should
 286                 jnz no_partition        ; be 00 or 80
 287                 mov eax,[di-8]          ; Partition offset (dword)
 288                 mov [bsHidden],eax
 289 no_partition:
 290 ;
 291 ; Get disk drive parameters (don't trust the superblock.)  Don't do this for
 292 ; floppy drives -- INT 13:08 on floppy drives will (may?) return info about
 293 ; what the *drive* supports, not about the *media*.  Fortunately floppy disks
 294 ; tend to have a fixed, well-defined geometry which is stored in the superblock.
 295 ;
 296                 ; DL == drive # still
 297                 mov ah,08h
 298                 int 13h
 299                 jc no_driveparm
 300                 and ah,ah
 301                 jnz no_driveparm
 302                 shr dx,8
 303                 inc dx                  ; Contains # of heads - 1
 304                 mov [bsHeads],dx
 305                 and cx,3fh
 306                 mov [bsSecPerTrack],cx
 307 no_driveparm:
 308 not_harddisk:
 309 ;
 310 ; Ready to enable interrupts, captain
 311 ;
 312                 sti
 313
 314 ;
 315 ; Do we have EBIOS (EDD)?
 316 ;
 317 eddcheck:
 318                 mov bx,55AAh
 319                 mov ah,41h              ; EDD existence query
 320                 mov dl,[DriveNumber]
 321                 int 13h
 322                 jc .noedd
 323                 cmp bx,0AA55h
 324                 jne .noedd
 325                 test cl,1               ; Extended disk access functionality set
 326                 jz .noedd
 327                 ;
 328                 ; We have EDD support...
 329                 ;
 330                 mov byte [getlinsec.jmp+1],(getlinsec_ebios-(getlinsec.jmp+2))
 331 .noedd:
 332
 333 ;
 334 ; Load the first sector of LDLINUX.SYS; this used to be all proper
 335 ; with parsing the superblock and root directory; it doesn't fit
 336 ; together with EBIOS support, unfortunately.
 337 ;
 338                 mov eax,[FirstSector]   ; Sector start
 339                 mov bx,ldlinux_sys      ; Where to load it
 340                 call getonesec
 341
 342                 ; Some modicum of integrity checking
 343                 cmp dword [ldlinux_magic+4],LDLINUX_MAGIC^HEXDATE
 344                 jne kaboom
 345
 346                 ; Go for it...
 347                 jmp ldlinux_ent
 348
 349 ;
 350 ; getonesec: get one disk sector
 351 ;
 352 getonesec:
 353                 mov bp,1                ; One sector
 354                 ; Fall through
 355
 356 ;
 357 ; getlinsec: load a sequence of BP floppy sector given by the linear sector
 358 ;            number in EAX into the buffer at ES:BX.  We try to optimize
 359 ;            by loading up to a whole track at a time, but the user
 360 ;            is responsible for not crossing a 64K boundary.
 361 ;            (Yes, BP is weird for a count, but it was available...)
 362 ;
 363 ;            On return, BX points to the first byte after the transferred
 364 ;            block.
 365 ;
 366 ;            This routine assumes CS == DS, and trashes most registers.
 367 ;
 368 ; Stylistic note: use "xchg" instead of "mov" when the source is a register
 369 ; that is dead from that point; this saves space.  However, please keep
 370 ; the order to dst,src to keep things sane.
 371 ;
 372 getlinsec:
 373                 add eax,[bsHidden]              ; Add partition offset
 374                 xor edx,edx                     ; Zero-extend LBA (eventually allow 64 bits)
 375
 376 .jmp:           jmp strict short getlinsec_cbios
 377
 378 ;
 379 ; getlinsec_ebios:
 380 ;
 381 ; getlinsec implementation for EBIOS (EDD)
 382 ;
 383 getlinsec_ebios:
 384 .loop:
 385                 push bp                         ; Sectors left
 386 .retry2:
 387                 call maxtrans                   ; Enforce maximum transfer size
 388                 movzx edi,bp                    ; Sectors we are about to read
 389                 mov cx,retry_count
 390 .retry:
 391
 392                 ; Form DAPA on stack
 393                 push edx
 394                 push eax
 395                 push es
 396                 push bx
 397                 push di
 398                 push word 16
 399                 mov si,sp
 400                 pushad
 401                 mov dl,[DriveNumber]
 402                 push ds
 403                 push ss
 404                 pop ds                          ; DS <- SS
 405                 mov ah,42h                      ; Extended Read
 406                 int 13h
 407                 pop ds
 408                 popad
 409                 lea sp,[si+16]                  ; Remove DAPA
 410                 jc .error
 411                 pop bp
 412                 add eax,edi                     ; Advance sector pointer
 413                 sub bp,di                       ; Sectors left
 414                 shl di,SECTOR_SHIFT             ; 512-byte sectors
 415                 add bx,di                       ; Advance buffer pointer
 416                 and bp,bp
 417                 jnz .loop
 418
 419                 ret
 420
 421 .error:
 422                 ; Some systems seem to get "stuck" in an error state when
 423                 ; using EBIOS.  Doesn't happen when using CBIOS, which is
 424                 ; good, since some other systems get timeout failures
 425                 ; waiting for the floppy disk to spin up.
 426
 427                 pushad                          ; Try resetting the device
 428                 xor ax,ax
 429                 mov dl,[DriveNumber]
 430                 int 13h
 431                 popad
 432                 loop .retry                     ; CX-- and jump if not zero
 433
 434                 ;shr word [MaxTransfer],1       ; Reduce the transfer size
 435                 ;jnz .retry2
 436
 437                 ; Total failure.  Try falling back to CBIOS.
 438                 mov byte [getlinsec.jmp+1],(getlinsec_cbios-(getlinsec.jmp+2))
 439                 ;mov byte [MaxTransfer],63      ; Max possibe CBIOS transfer
 440
 441                 pop bp
 442                 ; ... fall through ...
 443
 444 ;
 445 ; getlinsec_cbios:
 446 ;
 447 ; getlinsec implementation for legacy CBIOS
 448 ;
 449 getlinsec_cbios:
 450 .loop:
 451                 push edx
 452                 push eax
 453                 push bp
 454                 push bx
 455
 456                 movzx esi,word [bsSecPerTrack]
 457                 movzx edi,word [bsHeads]
 458                 ;
 459                 ; Dividing by sectors to get (track,sector): we may have
 460                 ; up to 2^18 tracks, so we need to use 32-bit arithmetric.
 461                 ;
 462                 div esi
 463                 xor cx,cx
 464                 xchg cx,dx              ; CX <- sector index (0-based)
 465                                         ; EDX <- 0
 466                 ; eax = track #
 467                 div edi                 ; Convert track to head/cyl
 468
 469                 ; We should test this, but it doesn't fit...
 470                 ; cmp eax,1023
 471                 ; ja .error
 472
 473                 ;
 474                 ; Now we have AX = cyl, DX = head, CX = sector (0-based),
 475                 ; BP = sectors to transfer, SI = bsSecPerTrack,
 476                 ; ES:BX = data target
 477                 ;
 478
 479                 call maxtrans                   ; Enforce maximum transfer size
 480
 481                 ; Must not cross track boundaries, so BP <= SI-CX
 482                 sub si,cx
 483                 cmp bp,si
 484                 jna .bp_ok
 485                 mov bp,si
 486 .bp_ok:
 487
 488                 shl ah,6                ; Because IBM was STOOPID
 489                                         ; and thought 8 bits were enough
 490                                         ; then thought 10 bits were enough...
 491                 inc cx                  ; Sector numbers are 1-based, sigh
 492                 or cl,ah
 493                 mov ch,al
 494                 mov dh,dl
 495                 mov dl,[DriveNumber]
 496                 xchg ax,bp              ; Sector to transfer count
 497                 mov ah,02h              ; Read sectors
 498                 mov bp,retry_count
 499 .retry:
 500                 pushad
 501                 int 13h
 502                 popad
 503                 jc .error
 504 .resume:
 505                 movzx ecx,al            ; ECX <- sectors transferred
 506                 shl ax,SECTOR_SHIFT     ; Convert sectors in AL to bytes in AX
 507                 pop bx
 508                 add bx,ax
 509                 pop bp
 510                 pop eax
 511                 pop edx
 512                 add eax,ecx
 513                 sub bp,cx
 514                 jnz .loop
 515                 ret
 516
 517 .error:
 518                 dec bp
 519                 jnz .retry
 520
 521                 xchg ax,bp              ; Sectors transferred <- 0
 522                 shr word [MaxTransfer],1
 523                 jnz .resume
 524                 ; Fall through to disk_error
 525
 526 ;
 527 ; kaboom: write a message and bail out.
 528 ;
 529 disk_error:
 530 kaboom:
 531                 xor si,si
 532                 mov ss,si
 533                 mov sp,StackBuf-4       ; Reset stack
 534                 mov ds,si               ; Reset data segment
 535                 pop dword [fdctab]      ; Restore FDC table
 536 .patch:                                 ; When we have full code, intercept here
 537                 mov si,bailmsg
 538
 539                 ; Write error message, this assumes screen page 0
 540 .loop:          lodsb
 541                 and al,al
 542                 jz .done
 543                 mov ah,0Eh              ; Write to screen as TTY
 544                 mov bx,0007h            ; Attribute
 545                 int 10h
 546                 jmp short .loop
 547 .done:
 548                 cbw                     ; AH <- 0
 549                 int 16h                 ; Wait for keypress
 550                 int 19h                 ; And try once more to boot...
 551 .norge:         jmp short .norge        ; If int 19h returned; this is the end
 552
 553 ;
 554 ; Truncate BP to MaxTransfer
 555 ;
 556 maxtrans:
 557                 cmp bp,[MaxTransfer]
 558                 jna .ok
 559                 mov bp,[MaxTransfer]
 560 .ok:            ret
 561
 562 ;
 563 ; Error message on failure
 564 ;
 565 bailmsg:        db 'Boot error', 0Dh, 0Ah, 0
 566
 567                 ; This fails if the boot sector overflows
 568                 zb 1F8h-($-$$)
 569
 570 FirstSector     dd 0xDEADBEEF                   ; Location of sector 1
 571 MaxTransfer     dw 0x007F                       ; Max transfer size
 572 bootsignature   dw 0AA55h
 573
 574 ;
 575 ; ===========================================================================
 576 ;  End of boot sector
 577 ; ===========================================================================
 578 ;  Start of LDLINUX.SYS
 579 ; ===========================================================================
 580
 581 ldlinux_sys:
 582
 583 syslinux_banner db 0Dh, 0Ah
 584 %if IS_MDSLINUX
 585                 db 'MDSLINUX '
 586 %else
 587                 db 'SYSLINUX '
 588 %endif
 589                 db version_str, ' ', date, ' ', 0
 590                 db 0Dh, 0Ah, 1Ah        ; EOF if we "type" this in DOS
 591
 592                 align 8, db 0
 593 ldlinux_magic   dd LDLINUX_MAGIC
 594                 dd LDLINUX_MAGIC^HEXDATE
 595
 596 ;
 597 ; This area is patched by the installer.  It is found by looking for
 598 ; LDLINUX_MAGIC, plus 8 bytes.
 599 ;
 600 patch_area:
 601 LDLDwords       dw 0            ; Total dwords starting at ldlinux_sys
 602 LDLSectors      dw 0            ; Number of sectors - (bootsec+this sec)
 603 CheckSum        dd 0            ; Checksum starting at ldlinux_sys
 604                                 ; value = LDLINUX_MAGIC - [sum of dwords]
 605
 606 ; Space for up to 64 sectors, the theoretical maximum
 607 SectorPtrs      times 64 dd 0
 608
 609 ldlinux_ent:
 610 ;
 611 ; Note that some BIOSes are buggy and run the boot sector at 07C0:0000
 612 ; instead of 0000:7C00 and the like.  We don't want to add anything
 613 ; more to the boot sector, so it is written to not assume a fixed
 614 ; value in CS, but we don't want to deal with that anymore from now
 615 ; on.
 616 ;
 617                 jmp 0:.next
 618 .next:
 619
 620 ;
 621 ; Tell the user we got this far
 622 ;
 623                 mov si,syslinux_banner
 624                 call writestr
 625
 626 ;
 627 ; Tell the user if we're using EBIOS or CBIOS
 628 ;
 629 print_bios:
 630                 mov si,cbios_name
 631                 cmp byte [getlinsec.jmp+1],(getlinsec_ebios-(getlinsec.jmp+2))
 632                 jne .cbios
 633                 mov si,ebios_name
 634 .cbios:
 635                 mov [BIOSName],si
 636                 call writestr
 637
 638                 section .bss
 639 %define HAVE_BIOSNAME 1
 640 BIOSName        resw 1
 641
 642                 section .text
 643 ;
 644 ; Now we read the rest of LDLINUX.SYS.  Don't bother loading the first
 645 ; sector again, though.
 646 ;
 647 load_rest:
 648                 mov si,SectorPtrs
 649                 mov bx,7C00h+2*SECTOR_SIZE      ; Where we start loading
 650                 mov cx,[LDLSectors]
 651
 652 .get_chunk:
 653                 jcxz .done
 654                 xor bp,bp
 655                 lodsd                           ; First sector of this chunk
 656
 657                 mov edx,eax
 658
 659 .make_chunk:
 660                 inc bp
 661                 dec cx
 662                 jz .chunk_ready
 663                 inc edx                         ; Next linear sector
 664                 cmp [si],edx                    ; Does it match
 665                 jnz .chunk_ready                ; If not, this is it
 666                 add si,4                        ; If so, add sector to chunk
 667                 jmp short .make_chunk
 668
 669 .chunk_ready:
 670                 call getlinsecsr
 671                 shl bp,SECTOR_SHIFT
 672                 add bx,bp
 673                 jmp .get_chunk
 674
 675 .done:
 676
 677 ;
 678 ; All loaded up, verify that we got what we needed.
 679 ; Note: the checksum field is embedded in the checksum region, so
 680 ; by the time we get to the end it should all cancel out.
 681 ;
 682 verify_checksum:
 683                 mov si,ldlinux_sys
 684                 mov cx,[LDLDwords]
 685                 mov edx,-LDLINUX_MAGIC
 686 .checksum:
 687                 lodsd
 688                 add edx,eax
 689                 loop .checksum
 690
 691                 and edx,edx                     ; Should be zero
 692                 jz all_read                     ; We're cool, go for it!
 693
 694 ;
 695 ; Uh-oh, something went bad...
 696 ;
 697                 mov si,checksumerr_msg
 698                 call writestr
 699                 jmp kaboom
 700
 701 ;
 702 ; -----------------------------------------------------------------------------
 703 ; Subroutines that have to be in the first sector
 704 ; -----------------------------------------------------------------------------
 705
 706 ;
 707 ;
 708 ; writestr: write a null-terminated string to the console
 709 ;           This assumes we're on page 0.  This is only used for early
 710 ;           messages, so it should be OK.
 711 ;
 712 writestr:
 713 .loop:          lodsb
 714                 and al,al
 715                 jz .return
 716                 mov ah,0Eh              ; Write to screen as TTY
 717                 mov bx,0007h            ; Attribute
 718                 int 10h
 719                 jmp short .loop
 720 .return:        ret
 721
 722
 723 ; getlinsecsr: save registers, call getlinsec, restore registers
 724 ;
 725 getlinsecsr:    pushad
 726                 call getlinsec
 727                 popad
 728                 ret
 729
 730 ;
 731 ; Checksum error message
 732 ;
 733 checksumerr_msg db ' Load error - ', 0  ; Boot failed appended
 734
 735 ;
 736 ; BIOS type string
 737 ;
 738 cbios_name      db 'CBIOS', 0
 739 ebios_name      db 'EBIOS', 0
 740
 741 ;
 742 ; Debug routine
 743 ;
 744 %ifdef debug
 745 safedumpregs:
 746                 cmp word [Debug_Magic],0D00Dh
 747                 jnz nc_return
 748                 jmp dumpregs
 749 %endif
 750
 751 rl_checkpt      equ $                           ; Must be <= 8000h
 752
 753 rl_checkpt_off  equ ($-$$)
 754 %ifndef DEPEND
 755 %if rl_checkpt_off > 400h
 756 %error "Sector 1 overflow"
 757 %endif
 758 %endif
 759
 760 ; ----------------------------------------------------------------------------
 761 ;  End of code and data that have to be in the first sector
 762 ; ----------------------------------------------------------------------------
 763
 764 all_read:
 765 ;
 766 ; Let the user (and programmer!) know we got this far.  This used to be
 767 ; in Sector 1, but makes a lot more sense here.
 768 ;
 769                 mov si,copyright_str
 770                 call writestr
 771
 772
 773 ;
 774 ; Insane hack to expand the superblock to dwords
 775 ;
 776 expand_super:
 777                 xor eax,eax
 778                 mov si,superblock
 779                 mov di,SuperInfo
 780                 mov cx,superinfo_size
 781 .loop:
 782                 lodsw
 783                 dec si
 784                 stosd                           ; Store expanded word
 785                 xor ah,ah
 786                 stosd                           ; Store expanded byte
 787                 loop .loop
 788
 789 ;
 790 ; Compute some information about this filesystem.
 791 ;
 792
 793 ; First, generate the map of regions
 794 genfatinfo:
 795                 mov edx,[bxSectors]
 796                 and dx,dx
 797                 jnz .have_secs
 798                 mov edx,[bsHugeSectors]
 799 .have_secs:
 800                 mov [TotalSectors],edx
 801
 802                 add edx,eax
 803                 mov [EndSector],edx
 804
 805                 mov eax,[bxResSectors]
 806                 mov [FAT],eax                   ; Beginning of FAT
 807                 mov edx,[bxFATsecs]
 808                 and dx,dx
 809                 jnz .have_fatsecs
 810                 mov edx,[bootsec+36]            ; FAT32 BPB_FATsz32
 811 .have_fatsecs:
 812                 imul edx,[bxFATs]
 813                 add eax,edx
 814                 mov [RootDirArea],eax           ; Beginning of root directory
 815                 mov [RootDir],eax               ; For FAT12/16 == root dir location
 816
 817                 mov edx,[bxRootDirEnts]
 818                 add dx,SECTOR_SIZE/32-1
 819                 shr dx,SECTOR_SHIFT-5
 820                 mov [RootDirSize],edx
 821                 add eax,edx
 822                 mov [DataArea],eax              ; Beginning of data area
 823
 824 ; Next, generate a cluster size shift count and mask
 825                 mov eax,[bxSecPerClust]
 826                 bsr cx,ax
 827                 mov [ClustShift],cl
 828                 push cx
 829                 add cl,9
 830                 mov [ClustByteShift],cl
 831                 pop cx
 832                 dec ax
 833                 mov [ClustMask],eax
 834                 inc ax
 835                 shl eax,9
 836                 mov [ClustSize],eax
 837
 838 ;
 839 ; FAT12, FAT16 or FAT28^H^H32?  This computation is fscking ridiculous.
 840 ;
 841 getfattype:
 842                 mov eax,[EndSector]
 843                 sub eax,[DataArea]
 844                 shr eax,cl                      ; cl == ClustShift
 845                 mov cl,nextcluster_fat12-(nextcluster+2)
 846                 cmp eax,4085                    ; FAT12 limit
 847                 jb .setsize
 848                 mov cl,nextcluster_fat16-(nextcluster+2)
 849                 cmp eax,65525                   ; FAT16 limit
 850                 jb .setsize
 851                 ;
 852                 ; FAT32, root directory is a cluster chain
 853                 ;
 854                 mov cl,[ClustShift]
 855                 mov eax,[bootsec+44]            ; Root directory cluster
 856                 sub eax,2
 857                 shl eax,cl
 858                 add eax,[DataArea]
 859                 mov [RootDir],eax
 860                 mov cl,nextcluster_fat28-(nextcluster+2)
 861 .setsize:
 862                 mov byte [nextcluster+1],cl
 863
 864 ;
 865 ; Common initialization code
 866 ;
 867 %include "cpuinit.inc"
 868 %include "init.inc"
 869
 870 ;
 871 ; Clear Files structures
 872 ;
 873                 mov di,Files
 874                 mov cx,(MAX_OPEN*open_file_t_size)/4
 875                 xor eax,eax
 876                 rep stosd
 877
 878 ;
 879 ; Initialize the metadata cache
 880 ;
 881                 call initcache
 882
 883 ;
 884 ; Now, everything is "up and running"... patch kaboom for more
 885 ; verbosity and using the full screen system
 886 ;
 887                 ; E9 = JMP NEAR
 888                 mov dword [kaboom.patch],0e9h+((kaboom2-(kaboom.patch+3)) << 8)
 889
 890 ;
 891 ; Now we're all set to start with our *real* business.  First load the
 892 ; configuration file (if any) and parse it.
 893 ;
 894 ; In previous versions I avoided using 32-bit registers because of a
 895 ; rumour some BIOSes clobbered the upper half of 32-bit registers at
 896 ; random.  I figure, though, that if there are any of those still left
 897 ; they probably won't be trying to install Linux on them...
 898 ;
 899 ; The code is still ripe with 16-bitisms, though.  Not worth the hassle
 900 ; to take'm out.  In fact, we may want to put them back if we're going
 901 ; to boot ELKS at some point.
 902 ;
 903
 904 ;
 905 ; Load configuration file
 906 ;
 907                 mov di,syslinux_cfg
 908                 call open
 909                 jz no_config_file
 910
 911 ;
 912 ; Now we have the config file open.  Parse the config file and
 913 ; run the user interface.
 914 ;
 915 %include "ui.inc"
 916
 917 ;
 918 ; Linux kernel loading code is common.
 919 ;
 920 %include "runkernel.inc"
 921
 922 ;
 923 ; COMBOOT-loading code
 924 ;
 925 %include "comboot.inc"
 926 %include "com32.inc"
 927 %include "cmdline.inc"
 928
 929 ;
 930 ; Boot sector loading code
 931 ;
 932 %include "bootsect.inc"
 933
 934 ;
 935 ; Abort loading code
 936 ;
 937 %include "abort.inc"
 938
 939 ;
 940 ; allocate_file: Allocate a file structure
 941 ;
 942 ;               If successful:
 943 ;                 ZF set
 944 ;                 BX = file pointer
 945 ;               In unsuccessful:
 946 ;                 ZF clear
 947 ;
 948 allocate_file:
 949                 TRACER 'a'
 950                 push cx
 951                 mov bx,Files
 952                 mov cx,MAX_OPEN
 953 .check:         cmp dword [bx], byte 0
 954                 je .found
 955                 add bx,open_file_t_size         ; ZF = 0
 956                 loop .check
 957                 ; ZF = 0 if we fell out of the loop
 958 .found:         pop cx
 959                 ret
 960
 961 ;
 962 ; searchdir:
 963 ;            Search the root directory for a pre-mangled filename in DS:DI.
 964 ;
 965 ;            NOTE: This file considers finding a zero-length file an
 966 ;            error.  This is so we don't have to deal with that special
 967 ;            case elsewhere in the program (most loops have the test
 968 ;            at the end).
 969 ;
 970 ;            If successful:
 971 ;               ZF clear
 972 ;               SI      = file pointer
 973 ;               DX:AX   = file length in bytes
 974 ;            If unsuccessful
 975 ;               ZF set
 976 ;
 977
 978 searchdir:
 979                 push bx
 980                 call allocate_file
 981                 jnz .alloc_failure
 982
 983                 push cx
 984                 push gs
 985                 push es
 986                 push ds
 987                 pop es                          ; ES = DS
 988
 989                 mov eax,[RootDir]               ; First root directory sector
 990
 991 .scansector:
 992                 call getcachesector
 993                 ; GS:SI now points to this sector
 994
 995                 mov cx,SECTOR_SIZE/32           ; 32 == directory entry size
 996 .scanentry:
 997                 cmp byte [gs:si],0
 998                 jz .failure                     ; Hit directory high water mark
 999                 push cx
1000                 push si
1001                 push di
1002                 mov cx,11
1003                 gs repe cmpsb
1004                 pop di
1005                 pop si
1006                 pop cx
1007                 jz .found
1008                 add si,32
1009                 loop .scanentry
1010
1011                 call nextsector
1012                 jnc .scansector                 ; CF is set if we're at end
1013
1014                 ; If we get here, we failed
1015 .failure:
1016                 pop es
1017                 pop gs
1018                 pop cx
1019 .alloc_failure:
1020                 pop bx
1021                 xor eax,eax                     ; ZF <- 1
1022                 ret
1023 .found:
1024                 mov eax,[gs:si+28]              ; File size
1025                 add eax,SECTOR_SIZE-1
1026                 shr eax,SECTOR_SHIFT
1027                 jz .failure                     ; Zero-length file
1028                 mov [bx+4],eax
1029
1030                 mov cl,[ClustShift]
1031                 mov dx,[gs:si+20]               ; High cluster word
1032                 shl edx,16
1033                 mov dx,[gs:si+26]               ; Low cluster word
1034                 sub edx,2
1035                 shl edx,cl
1036                 add edx,[DataArea]
1037                 mov [bx],edx                    ; Starting sector
1038
1039                 mov eax,[gs:si+28]              ; File length again
1040                 mov dx,[gs:si+30]               ; 16-bitism, sigh
1041                 mov si,bx
1042                 and eax,eax                     ; ZF <- 0
1043
1044                 pop es
1045                 pop gs
1046                 pop cx
1047                 pop bx
1048                 ret
1049
1050 ;
1051 ; writechr:     Write a single character in AL to the console without
1052 ;               mangling any registers; handle video pages correctly.
1053 ;
1054 writechr:
1055                 call write_serial       ; write to serial port if needed
1056                 pushfd
1057                 test byte [cs:DisplayCon], 01h
1058                 jz .nothing
1059                 pushad
1060                 mov ah,0Eh
1061                 mov bl,07h              ; attribute
1062                 mov bh,[cs:BIOS_page]   ; current page
1063                 int 10h
1064                 popad
1065 .nothing:
1066                 popfd
1067                 ret
1068
1069 ;
1070 ;
1071 ; kaboom2: once everything is loaded, replace the part of kaboom
1072 ;          starting with "kaboom.patch" with this part
1073
1074 kaboom2:
1075                 mov si,err_bootfailed
1076                 call cwritestr
1077                 call getchar
1078                 call vgaclearmode
1079                 int 19h                 ; And try once more to boot...
1080 .norge:         jmp short .norge        ; If int 19h returned; this is the end
1081
1082 ;
1083 ; mangle_name: Mangle a DOS filename pointed to by DS:SI into a buffer pointed
1084 ;              to by ES:DI; ends on encountering any whitespace
1085 ;
1086
1087 mangle_name:
1088                 mov cx,11                       ; # of bytes to write
1089 mn_loop:
1090                 lodsb
1091                 cmp al,' '                      ; If control or space, end
1092                 jna mn_end
1093                 cmp al,'.'                      ; Period -> space-fill
1094                 je mn_is_period
1095                 cmp al,'a'
1096                 jb mn_not_lower
1097                 cmp al,'z'
1098                 ja mn_not_uslower
1099                 sub al,020h
1100                 jmp short mn_not_lower
1101 mn_is_period:   mov al,' '                      ; We need to space-fill
1102 mn_period_loop: cmp cx,3                        ; If <= 3 characters left
1103                 jbe mn_loop                     ; Just ignore it
1104                 stosb                           ; Otherwise, write a period
1105                 loop mn_period_loop             ; Dec CX and (always) jump
1106 mn_not_uslower: cmp al,ucase_low
1107                 jb mn_not_lower
1108                 cmp al,ucase_high
1109                 ja mn_not_lower
1110                 mov bx,ucase_tab-ucase_low
1111                 cs xlatb
1112 mn_not_lower:   stosb
1113                 loop mn_loop                    ; Don't continue if too long
1114 mn_end:
1115                 mov al,' '                      ; Space-fill name
1116                 rep stosb                       ; Doesn't do anything if CX=0
1117                 ret                             ; Done
1118
1119 ;
1120 ; Upper-case table for extended characters; this is technically code page 865,
1121 ; but code page 437 users will probably not miss not being able to use the
1122 ; cent sign in kernel images too much :-)
1123 ;
1124 ; The table only covers the range 129 to 164; the rest we can deal with.
1125 ;
1126 ucase_low       equ 129
1127 ucase_high      equ 164
1128 ucase_tab       db 154, 144, 'A', 142, 'A', 143, 128, 'EEEIII'
1129                 db 142, 143, 144, 146, 146, 'O', 153, 'OUUY', 153, 154
1130                 db 157, 156, 157, 158, 159, 'AIOU', 165
1131
1132 ;
1133 ; unmangle_name: Does the opposite of mangle_name; converts a DOS-mangled
1134 ;                filename to the conventional representation.  This is needed
1135 ;                for the BOOT_IMAGE= parameter for the kernel.
1136 ;                NOTE: A 13-byte buffer is mandatory, even if the string is
1137 ;                known to be shorter.
1138 ;
1139 ;                DS:SI -> input mangled file name
1140 ;                ES:DI -> output buffer
1141 ;
1142 ;                On return, DI points to the first byte after the output name,
1143 ;                which is set to a null byte.
1144 ;
1145 unmangle_name:
1146                 push si                 ; Save pointer to original name
1147                 mov cx,8
1148                 mov bp,di
1149 un_copy_body:   lodsb
1150                 call lower_case
1151                 stosb
1152                 cmp al,' '
1153                 jbe un_cb_space
1154                 mov bp,di               ; Position of last nonblank+1
1155 un_cb_space:    loop un_copy_body
1156                 mov di,bp
1157                 mov al,'.'              ; Don't save
1158                 stosb
1159                 mov cx,3
1160 un_copy_ext:    lodsb
1161                 call lower_case
1162                 stosb
1163                 cmp al,' '
1164                 jbe un_ce_space
1165                 mov bp,di
1166 un_ce_space:    loop un_copy_ext
1167                 mov di,bp
1168                 mov byte [es:di], 0
1169                 pop si
1170                 ret
1171
1172 ;
1173 ; lower_case: Lower case a character in AL
1174 ;
1175 lower_case:
1176                 cmp al,'A'
1177                 jb lc_ret
1178                 cmp al,'Z'
1179                 ja lc_1
1180                 or al,20h
1181                 ret
1182 lc_1:           cmp al,lcase_low
1183                 jb lc_ret
1184                 cmp al,lcase_high
1185                 ja lc_ret
1186                 push bx
1187                 mov bx,lcase_tab-lcase_low
1188                 cs xlatb
1189                 pop bx
1190 lc_ret:         ret
1191
1192 ;
1193 ; getfssec_edx: Get multiple sectors from a file
1194 ;
1195 ;       This routine makes sure the subtransfers do not cross a 64K boundary,
1196 ;       and will correct the situation if it does, UNLESS *sectors* cross
1197 ;       64K boundaries.
1198 ;
1199 ;       ES:BX   -> Buffer
1200 ;       EDX     -> Current sector number
1201 ;       CX      -> Sector count (0FFFFh = until end of file)
1202 ;                  Must not exceed the ES segment
1203 ;       Returns EDX=0, CF=1 on EOF (not necessarily error)
1204 ;       All arguments are advanced to reflect data read.
1205 ;
1206 getfssec_edx:
1207                 push ebp
1208                 push eax
1209 .getfragment:
1210                 xor ebp,ebp                     ; Fragment sector count
1211                 push edx                        ; Starting sector pointer
1212 .getseccnt:
1213                 inc bp
1214                 dec cx
1215                 jz .do_read
1216                 xor eax,eax
1217                 mov ax,es
1218                 shl ax,4
1219                 add ax,bx                       ; Now AX = how far into 64K block we are
1220                 not ax                          ; Bytes left in 64K block
1221                 inc eax
1222                 shr eax,SECTOR_SHIFT            ; Sectors left in 64K block
1223                 cmp bp,ax
1224                 jnb .do_read                    ; Unless there is at least 1 more sector room...
1225                 mov eax,edx                     ; Current sector
1226                 inc edx                         ; Predict it's the linearly next sector
1227                 call nextsector
1228                 jc .do_read
1229                 cmp edx,eax                     ; Did it match?
1230                 jz .getseccnt
1231 .do_read:
1232                 pop eax                         ; Starting sector pointer
1233                 call getlinsecsr
1234                 lea eax,[eax+ebp-1]             ; This is the last sector actually read
1235                 shl bp,9
1236                 add bx,bp                       ; Adjust buffer pointer
1237                 call nextsector
1238                 jc .eof
1239                 mov edx,eax
1240                 and cx,cx
1241                 jnz .getfragment
1242 .done:
1243                 pop eax
1244                 pop ebp
1245                 ret
1246 .eof:
1247                 xor edx,edx
1248                 stc
1249                 jmp .done
1250
1251 ;
1252 ; getfssec: Get multiple sectors from a file
1253 ;
1254 ;       Same as above, except SI is a pointer to a open_file_t
1255 ;
1256 ;       ES:BX   -> Buffer
1257 ;       DS:SI   -> Pointer to open_file_t
1258 ;       CX      -> Sector count (0FFFFh = until end of file)
1259 ;                  Must not exceed the ES segment
1260 ;       Returns CF=1 on EOF (not necessarily error)
1261 ;       All arguments are advanced to reflect data read.
1262 ;
1263 getfssec:
1264                 push edx
1265                 movzx edx,cx
1266                 cmp edx,[si+4]
1267                 jbe .sizeok
1268                 mov edx,[si+4]
1269                 mov cx,dx
1270 .sizeok:
1271                 sub [si+4],edx
1272                 mov edx,[si]
1273                 call getfssec_edx
1274                 mov [si],edx
1275                 pop edx
1276                 ret
1277
1278 ;
1279 ; nextcluster: Advance a cluster pointer in EDI to the next cluster
1280 ;              pointed at in the FAT tables.  CF=0 on return if end of file.
1281 ;
1282 nextcluster:
1283                 jmp strict short nextcluster_fat28      ; This gets patched
1284
1285 nextcluster_fat12:
1286                 push eax
1287                 push edx
1288                 push bx
1289                 push cx
1290                 push si
1291                 mov edx,edi
1292                 shr edi,1
1293                 pushf                   ; Save the shifted-out LSB (=CF)
1294                 add edx,edi
1295                 mov eax,edx
1296                 shr eax,9
1297                 call getfatsector
1298                 mov bx,dx
1299                 and bx,1FFh
1300                 mov cl,[gs:si+bx]
1301                 inc edx
1302                 mov eax,edx
1303                 shr eax,9
1304                 call getfatsector
1305                 mov bx,dx
1306                 and bx,1FFh
1307                 mov ch,[gs:si+bx]
1308                 popf
1309                 jnc .even
1310                 shr cx,4
1311 .even:          and cx,0FFFh
1312                 movzx edi,cx
1313                 cmp di,0FF0h
1314                 pop si
1315                 pop cx
1316                 pop bx
1317                 pop edx
1318                 pop eax
1319                 ret
1320
1321 ;
1322 ; FAT16 decoding routine.
1323 ;
1324 nextcluster_fat16:
1325                 push eax
1326                 push si
1327                 push bx
1328                 mov eax,edi
1329                 shr eax,SECTOR_SHIFT-1
1330                 call getfatsector
1331                 mov bx,di
1332                 add bx,bx
1333                 and bx,1FEh
1334                 movzx edi,word [gs:si+bx]
1335                 cmp di,0FFF0h
1336                 pop bx
1337                 pop si
1338                 pop eax
1339                 ret
1340 ;
1341 ; FAT28 ("FAT32") decoding routine.
1342 ;
1343 nextcluster_fat28:
1344                 push eax
1345                 push si
1346                 push bx
1347                 mov eax,edi
1348                 shr eax,SECTOR_SHIFT-2
1349                 call getfatsector
1350                 mov bx,di
1351                 add bx,bx
1352                 add bx,bx
1353                 and bx,1FCh
1354                 mov edi,dword [gs:si+bx]
1355                 and edi,0FFFFFFFh       ; 28 bits only
1356                 cmp edi,0FFFFFF0h
1357                 pop bx
1358                 pop si
1359                 pop eax
1360                 ret
1361
1362 ;
1363 ; nextsector:   Given a sector in EAX on input, return the next sector
1364 ;               of the same filesystem object, which may be the root
1365 ;               directory or a cluster chain.  Returns  EOF.
1366 ;
1367 ;               Assumes CS == DS.
1368 ;
1369 nextsector:
1370                 push edi
1371                 push edx
1372                 mov edx,[DataArea]
1373                 mov edi,eax
1374                 sub edi,edx
1375                 jae .isdata
1376
1377                 ; Root directory
1378                 inc eax
1379                 cmp eax,edx
1380                 cmc
1381                 jmp .done
1382
1383 .isdata:
1384                 not edi
1385                 test edi,[ClustMask]
1386                 jz .endcluster
1387
1388                 ; It's not the final sector in a cluster
1389                 inc eax
1390                 jmp .done
1391
1392 .endcluster:
1393                 push gs                 ; nextcluster trashes gs
1394                 push cx
1395                 not edi
1396                 mov cl,[ClustShift]
1397                 shr edi,cl
1398                 add edi,2
1399
1400                 ; Now EDI contains the cluster number
1401                 call nextcluster
1402                 cmc
1403                 jc .exit                ; There isn't anything else...
1404
1405                 ; New cluster number now in EDI
1406                 sub edi,2
1407                 shl edi,cl              ; CF <- 0, unless something is very wrong
1408                 lea eax,[edi+edx]
1409 .exit:
1410                 pop cx
1411                 pop gs
1412 .done:
1413                 pop edx
1414                 pop edi
1415                 ret
1416
1417 ;
1418 ; getfatsector: Check for a particular sector (in EAX) in the FAT cache,
1419 ;               and return a pointer in GS:SI, loading it if needed.
1420 ;
1421 ;               Assumes CS == DS.
1422 ;
1423 getfatsector:
1424                 add eax,[FAT]           ; FAT starting address
1425                 jmp getcachesector
1426
1427 ; -----------------------------------------------------------------------------
1428 ;  Common modules
1429 ; -----------------------------------------------------------------------------
1430
1431 %include "getc.inc"             ; getc et al
1432 %include "conio.inc"            ; Console I/O
1433 %include "writestr.inc"         ; String output
1434 %include "parseconfig.inc"      ; High-level config file handling
1435 %include "parsecmd.inc"         ; Low-level config file handling
1436 %include "bcopy32.inc"          ; 32-bit bcopy
1437 %include "loadhigh.inc"         ; Load a file into high memory
1438 %include "font.inc"             ; VGA font stuff
1439 %include "graphics.inc"         ; VGA graphics
1440 %include "highmem.inc"          ; High memory sizing
1441 %include "strcpy.inc"           ; strcpy()
1442 %include "cache.inc"            ; Metadata disk cache
1443
1444 ; -----------------------------------------------------------------------------
1445 ;  Begin data section
1446 ; -----------------------------------------------------------------------------
1447
1448                 section .data
1449 ;
1450 ; Lower-case table for codepage 865
1451 ;
1452 lcase_low       equ 128
1453 lcase_high      equ 165
1454 lcase_tab       db 135, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138
1455                 db 139, 140, 141, 132, 134, 130, 145, 145, 147, 148, 149
1456                 db 150, 151, 152, 148, 129, 155, 156, 155, 158, 159, 160
1457                 db 161, 162, 163, 164, 164
1458
1459 copyright_str   db ' Copyright (C) 1994-', year, ' H. Peter Anvin'
1460                 db CR, LF, 0
1461 boot_prompt     db 'boot: ', 0
1462 wipe_char       db BS, ' ', BS, 0
1463 err_notfound    db 'Could not find kernel image: ',0
1464 err_notkernel   db CR, LF, 'Invalid or corrupt kernel image.', CR, LF, 0
1465 err_noram       db 'It appears your computer has less than '
1466                 asciidec dosram_k
1467                 db 'K of low ("DOS")'
1468                 db CR, LF
1469                 db 'RAM.  Linux needs at least this amount to boot.  If you get'
1470                 db CR, LF
1471                 db 'this message in error, hold down the Ctrl key while'
1472                 db CR, LF
1473                 db 'booting, and I will take your word for it.', CR, LF, 0
1474 err_badcfg      db 'Unknown keyword in syslinux.cfg.', CR, LF, 0
1475 err_noparm      db 'Missing parameter in syslinux.cfg.', CR, LF, 0
1476 err_noinitrd    db CR, LF, 'Could not find ramdisk image: ', 0
1477 err_nohighmem   db 'Not enough memory to load specified kernel.', CR, LF, 0
1478 err_highload    db CR, LF, 'Kernel transfer failure.', CR, LF, 0
1479 err_oldkernel   db 'Cannot load a ramdisk with an old kernel image.'
1480                 db CR, LF, 0
1481 err_notdos      db ': attempted DOS system call', CR, LF, 0
1482 err_comlarge    db 'COMBOOT image too large.', CR, LF, 0
1483 err_a20         db CR, LF, 'A20 gate not responding!', CR, LF, 0
1484 err_bootfailed  db CR, LF, 'Boot failed: please change disks and press '
1485                 db 'a key to continue.', CR, LF, 0
1486 ready_msg       db 'Ready.', CR, LF, 0
1487 crlfloading_msg db CR, LF
1488 loading_msg     db 'Loading ', 0
1489 dotdot_msg      db '.'
1490 dot_msg         db '.', 0
1491 aborted_msg     db ' aborted.'                  ; Fall through to crlf_msg!
1492 crlf_msg        db CR, LF
1493 null_msg        db 0
1494 crff_msg        db CR, FF, 0
1495 syslinux_cfg    db 'SYSLINUXCFG'                ; Mangled form
1496 ConfigName      db 'syslinux.cfg',0             ; Unmangled form
1497 %if IS_MDSLINUX
1498 manifest        db 'MANIFEST   '
1499 %endif
1500 ;
1501 ; Command line options we'd like to take a look at
1502 ;
1503 ; mem= and vga= are handled as normal 32-bit integer values
1504 initrd_cmd      db 'initrd='
1505 initrd_cmd_len  equ 7
1506
1507 ;
1508 ; Config file keyword table
1509 ;
1510 %include "keywords.inc"
1511
1512 ;
1513 ; Extensions to search for (in *forward* order).
1514 ;
1515 exten_table:    db 'CBT',0              ; COMBOOT (specific)
1516                 db 'BSS',0              ; Boot Sector (add superblock)
1517                 db 'BS ',0              ; Boot Sector
1518                 db 'COM',0              ; COMBOOT (same as DOS)
1519                 db 'C32',0              ; COM32
1520 exten_table_end:
1521                 dd 0, 0                 ; Need 8 null bytes here
1522
1523 ;
1524 ; Misc initialized (data) variables
1525 ;
1526 %ifdef debug                            ; This code for debugging only
1527 debug_magic     dw 0D00Dh               ; Debug code sentinel
1528 %endif
1529
1530                 alignb 4, db 0
1531 BufSafe         dw trackbufsize/SECTOR_SIZE     ; Clusters we can load into trackbuf
1532 BufSafeSec      dw trackbufsize/SECTOR_SIZE     ; = how many sectors?
1533 BufSafeBytes    dw trackbufsize         ; = how many bytes?
1534 EndOfGetCBuf    dw getcbuf+trackbufsize ; = getcbuf+BufSafeBytes
1535 %ifndef DEPEND
1536 %if ( trackbufsize % SECTOR_SIZE ) != 0
1537 %error trackbufsize must be a multiple of SECTOR_SIZE
1538 %endif
1539 %endif