src/pseudo.S

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