| [1141c1a] | 1 | #
|
|---|
| 2 | # Copyright (C) 2001-2004 Jakub Jermar
|
|---|
| 3 | # All rights reserved.
|
|---|
| 4 | #
|
|---|
| 5 | # Redistribution and use in source and binary forms, with or without
|
|---|
| 6 | # modification, are permitted provided that the following conditions
|
|---|
| 7 | # are met:
|
|---|
| 8 | #
|
|---|
| 9 | # - Redistributions of source code must retain the above copyright
|
|---|
| 10 | # notice, this list of conditions and the following disclaimer.
|
|---|
| 11 | # - Redistributions in binary form must reproduce the above copyright
|
|---|
| 12 | # notice, this list of conditions and the following disclaimer in the
|
|---|
| 13 | # documentation and/or other materials provided with the distribution.
|
|---|
| 14 | # - The name of the author may not be used to endorse or promote products
|
|---|
| 15 | # derived from this software without specific prior written permission.
|
|---|
| 16 | #
|
|---|
| 17 | # THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
|
|---|
| 18 | # IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
|
|---|
| 19 | # OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
|
|---|
| 20 | # IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
|
|---|
| 21 | # INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
|
|---|
| 22 | # NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
|
|---|
| 23 | # DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
|
|---|
| 24 | # THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
|
|---|
| 25 | # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
|
|---|
| 26 | # THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
|
|---|
| 27 | #
|
|---|
| 28 |
|
|---|
| 29 | # This is a very primitive boot.s
|
|---|
| 30 |
|
|---|
| 31 | # It assumes that the first sector of the kernel image is found
|
|---|
| 32 | # on head 0, track 0, sector 2 of the first floppy drive (1440K).
|
|---|
| 33 | # Next kernel sectors follow on disk sector 3, 4, ...
|
|---|
| 34 | #
|
|---|
| 35 |
|
|---|
| 36 |
|
|---|
| 37 | # KERNEL_SIZE is passed from the outside to the preprocessor
|
|---|
| 38 | #if (KERNEL_SIZE%512>0)
|
|---|
| 39 | #define TAIL 1
|
|---|
| 40 | #else
|
|---|
| 41 | #define TAIL 0
|
|---|
| 42 | #endif
|
|---|
| 43 |
|
|---|
| 44 | #define SECTORS (KERNEL_SIZE/512+TAIL)
|
|---|
| 45 |
|
|---|
| 46 | .text
|
|---|
| 47 | .global _start_0x7c00
|
|---|
| 48 |
|
|---|
| 49 | .code16
|
|---|
| 50 | _start_0x7c00:
|
|---|
| 51 | xorw %ax,%ax # reset, %al will be used below
|
|---|
| 52 | movw %ax,%dx # fd0, %dh and %dl will be used below
|
|---|
| 53 | movw %dx,%ds
|
|---|
| 54 |
|
|---|
| 55 | movw %dx,%ss # initialize stack
|
|---|
| 56 | movw $stack,%sp
|
|---|
| 57 |
|
|---|
| 58 | int $0x13 # reset floppy
|
|---|
| 59 | jc stop_trying
|
|---|
| 60 |
|
|---|
| 61 | movw %dx,%ds
|
|---|
| 62 | movw %dx,%ss
|
|---|
| 63 | movw $0x7c00,%sp
|
|---|
| 64 | movw $0xffe0,%si # after next increment, %si will become 0x0000
|
|---|
| 65 | movw %si,%es
|
|---|
| 66 | movw $0x8000,%bx # at %es:%bx
|
|---|
| 67 |
|
|---|
| 68 | movl $(SECTORS),%edi
|
|---|
| 69 |
|
|---|
| 70 | read_next:
|
|---|
| 71 | test %edi,%edi
|
|---|
| 72 | jnz read_sectors
|
|---|
| 73 |
|
|---|
| 74 | movb $12,%al
|
|---|
| 75 | movw $0x3f2,%dx
|
|---|
| 76 | outb %al,%dx
|
|---|
| 77 |
|
|---|
| 78 | movb $('$'),%al
|
|---|
| 79 | call echo_mark
|
|---|
| 80 |
|
|---|
| 81 | jmpl $0,$0x8000
|
|---|
| 82 |
|
|---|
| 83 | read_sectors:
|
|---|
| 84 | movb $('.'),%al
|
|---|
| 85 | call echo_mark
|
|---|
| 86 |
|
|---|
| 87 | decl %edi
|
|---|
| 88 | incw logical_sector
|
|---|
| 89 | movw %es,%si
|
|---|
| 90 | addw $0x20,%si
|
|---|
| 91 | movw %si,%es
|
|---|
| 92 |
|
|---|
| 93 | movw logical_sector,%ax
|
|---|
| 94 | divb sectors
|
|---|
| 95 |
|
|---|
| 96 | movb %ah,%cl
|
|---|
| 97 | incb %cl # sector
|
|---|
| 98 |
|
|---|
| 99 | movb %al,%ch
|
|---|
| 100 | shrb $1,%ch # track
|
|---|
| 101 |
|
|---|
| 102 | movb %al,%dh
|
|---|
| 103 | andb $1,%dh # head
|
|---|
| 104 |
|
|---|
| 105 | movw $0x0201,%ax
|
|---|
| 106 | int $0x13
|
|---|
| 107 | jnc read_next
|
|---|
| 108 |
|
|---|
| 109 | movb $('R'),%al
|
|---|
| 110 | call echo_mark
|
|---|
| 111 |
|
|---|
| 112 | xorw %ax,%ax # try to reset
|
|---|
| 113 | movw %ax,%dx # fd0
|
|---|
| 114 | int $0x13
|
|---|
| 115 | jnc read_next
|
|---|
| 116 |
|
|---|
| 117 | stop_trying:
|
|---|
| 118 | movb $('F'),%al
|
|---|
| 119 | call echo_mark
|
|---|
| 120 |
|
|---|
| 121 | cli
|
|---|
| 122 | hlt
|
|---|
| 123 |
|
|---|
| 124 | CH=4
|
|---|
| 125 | echo_mark:
|
|---|
| 126 | push %bp
|
|---|
| 127 | movw %sp,%bp
|
|---|
| 128 | pusha
|
|---|
| 129 |
|
|---|
| 130 | movb $0xe,%ah
|
|---|
| 131 | movb $7,%bl
|
|---|
| 132 | int $0x10
|
|---|
| 133 |
|
|---|
| 134 | popa
|
|---|
| 135 | pop %bp
|
|---|
| 136 | ret
|
|---|
| 137 |
|
|---|
| 138 | # current logical sector from the beginning of the disk
|
|---|
| 139 | logical_sector:
|
|---|
| 140 | .word 0
|
|---|
| 141 |
|
|---|
| 142 | # number of sectors per track on 1440 floppy
|
|---|
| 143 | sectors:
|
|---|
| 144 | .byte 18
|
|---|
| 145 |
|
|---|
| 146 | # boot floppy signature
|
|---|
| 147 | .org 0x1fe
|
|---|
| 148 | boot_floppy_signature:
|
|---|
| 149 | .byte 0x55
|
|---|
| 150 | .byte 0xaa
|
|---|
| 151 | stack:
|
|---|
