src/pseudo.S

   1 ;  pseudo.S  -  Produce a pseudo kernel header
   2 ;
   3 ;               Useful for booting arbitrary
   4 ;               binary images at 0x1000:0000
   5 ;
   6 ;  Copyright 2002-2005 John Coffman
   7 ;  Copyright 2009-2011 Joachim Wiedorn
   8 ;  All rights reserved.
   9 ;
  10 ;  Licensed under the terms contained in the file 'COPYING'
  11 ;  in the source directory.
  12 ;
  13
  14 #define DEBUG 0
  15 #define DELL_DIRTY_HACK
  16
  17
  18 SYSSEG  =  0x1000       ; DEF_SYSSEG
  19 SETUPSEG = 0x9020       ; DEF_SETUPSEG
  20
  21 CL_MAGIC_ADDR   = 0x20                  ! command line magic number
  22 CL_MAGIC        = 0xa33f                ! very unusual command sequence
  23 CL_OFFSET       = 0x22                  ! command line offset
  24 CL_LENGTH       = 256                   ! maximum length
  25
  26                 .text
  27 #if 0
  28 .globl  _main
  29 _main:
  30 #endif
  31                 .globl  zero
  32 zero:
  33
  34 ; we want this to look like a bootable kernel image
  35 ; so we include the following header
  36 ;
  37                 jmp     begin
  38                 .ascii  "HdrS"          ; looks like a real kernel
  39                 .word   0x0200          ; header format version number
  40                 .word   0,0             ; realmode switch, SETUPSEG
  41                 .word   SYSSEG          ; SYSSEG -- load at 1000:0000
  42                 .word   id_string
  43                 .byte   0               ; type of loader
  44                 .byte   0               ; flags 0=load low
  45                 .word   2*512           ; move size: 2 sectors
  46                 dd      0x10000         ; load us here
  47                 dd      0               ; ramdisk image
  48                 dd      0               ; ramdisk size
  49                 .word   bs_helper,SETUPSEG      ; kludge???
  50 ;;              .word   modelist+1024   ; heap end pointer
  51 ;----------end of header------------
  52
  53 begin:
  54         xor     di,di
  55         cmp     word ptr [CL_MAGIC_ADDR],#CL_MAGIC
  56         jne     gotoit
  57         mov     di,[CL_OFFSET]
  58 gotoit:
  59         jmpi    0000,SYSSEG                     ; jmp to 0x1000:0000
  60
  61
  62 bs_helper:      int     0x19                    ;label here for kludge
  63
  64
  65 id_string:      .ascii  "pseudo.b"
  66                 .byte   0
  67
  68                 .blkb   zero+512-*
  69
  70 modelist:
  71
  72 theend: