mirror of
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Release cleanup
svn path=/trunk/; revision=16
This commit is contained in:
Rex Jolliff
parent
1189c35dd7
commit
4ef8280497
1 changed files with 0 additions and 640 deletions
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1 ;
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2 ; File:
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3 ; boot.asm
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4 ; Description:
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5 ; DOS-C boot
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6 ;
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7 ; Copyright (c) 1997;
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8 ; Svante Frey
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9 ; All Rights Reserved
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10 ;
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11 ; This file is part of DOS-C.
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12 ;
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13 ; DOS-C is free software; you can redistribute it and/or
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14 ; modify it under the terms of the GNU General Public License
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15 ; as published by the Free Software Foundation; either version
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16 ; 2, or (at your option) any later version.
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17 ;
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18 ; DOS-C is distributed in the hope that it will be useful, but
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19 ; WITHOUT ANY WARRANTY; without even the implied warranty of
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20 ; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See
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21 ; the GNU General Public License for more details.
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22 ;
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23 ; You should have received a copy of the GNU General Public
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24 ; License along with DOS-C; see the file COPYING. If not,
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25 ; write to the Free Software Foundation, 675 Mass Ave,
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26 ; Cambridge, MA 02139, USA.
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27 ;
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28 ; $Logfile: C:/dos-c/src/boot/boot.asv $
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29 ;
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30 ; $Header: /cygdrive/c/RCVS/CVS/ReactOS/reactos/loaders/boot/Attic/boot.lst,v 1.2 1998/08/12 22:43:38 rosmgr Exp $
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31 ;
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32 ; $Log: boot.lst,v $
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32 ; Revision 1.2 1998/08/12 22:43:38 rosmgr
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32 ; Update from the kernel team
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32 ;
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33 ;
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34 ; Rev 1.5 10 Jan 1997 4:58:06 patv
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35 ; Corrected copyright
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36 ;
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37 ; Rev 1.4 10 Jan 1997 4:52:50 patv
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38 ; Re-written to support C drive and eliminate restrictions on IPL.SYS
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39 ;
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40 ; Rev 1.3 29 Aug 1996 13:06:50 patv
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41 ; Bug fixes for v0.91b
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42 ;
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43 ; Rev 1.2 01 Sep 1995 17:56:44 patv
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44 ; First GPL release.
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45 ;
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46 ; Rev 1.1 30 Jul 1995 20:37:38 patv
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47 ; Initialized stack before use.
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48 ;
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49 ; Rev 1.0 02 Jul 1995 10:57:52 patv
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50 ; Initial revision.
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51 ;
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52
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53 section .text
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54
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55 org 0
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56 00000000 E93D00 Entry: jmp real_start
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57
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58 ; bp is initialized to 7c00h
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59 %define oem [bp+3]
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60 %define bytesPerSector [bp+0bh]
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61 %define sectPerCluster [bp+0dh]
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62 %define resSectors [bp+0eh]
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63 %define nFats [bp+10h]
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64 %define nRootDir [bp+11h]
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65 %define nSectors [bp+13h]
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66 %define MID [bp+15h]
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67 %define sectPerFat [bp+16h]
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68 %define sectPerTrack [bp+18h]
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69 %define nHeads [bp+1ah]
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70 %define nHidden [bp+1ch]
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71 %define nHidden_hi [bp+1eh]
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72 %define nSectorHuge [bp+20h]
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73 %define drive [bp+24h]
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74 %define extBoot [bp+26h]
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75 %define volid [bp+27h]
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76 %define vollabel [bp+2bh]
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77 %define filesys 36h
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78
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79 LOADSEG equ 2000h
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80
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81 FATBUF equ 4000h ; offset of temporary buffer for FAT
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82 ; chain
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83 RETRYCOUNT equ 5 ; number of retries on disk errors
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84
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85 ; Some extra variables that are created on the stack frame
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86
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87 %define fat_start [bp-4] ; first FAT sector
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88 %define fat_start_hi [bp-2]
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89 %define root_dir_start [bp-8] ; first root directory sector
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90 %define root_dir_start_hi [bp-6]
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91 %define data_start [bp-12] ; first data sector
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92 %define data_start_hi [bp-10]
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93
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94 ;
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95 ; Include macros for filesystem access
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96 ;
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97 %include "boot.inc"
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98 <1> ; To save space, functions that are just called once are
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99 <1> ; implemented as macros instead. Four bytes are saved by
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100 <1> ; avoiding the call / ret instructions.
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101 <1>
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102 <1>
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103 <1> ; FINDFILE: Searches for the file in the root directory.
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104 <1> ;
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105 <1> ; Returns:
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106 <1> ;
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107 <1> ; If file not found: CF set
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108 <1> ;
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109 <1> ; If file found: CF clear
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110 <1> ; AX = first cluster of file
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111 <1>
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112 <1>
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113 <1> %macro FINDFILE 0
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114 <1> ; First, read the whole root directory
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115 <1> ; into the temporary buffer.
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116 <1>
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117 <1> mov ax, word root_dir_start
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118 <1> mov dx, word root_dir_start_hi
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119 <1> mov di, nRootDir
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120 <1> xor bx, bx
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121 <1> mov es, tempbuf
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122 <1> call readDisk
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123 <1> jc ffDone
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124 <1>
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125 <1> xor di, di
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126 <1>
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127 <1> next_entry: mov cx, 11
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128 <1> mov si, filename+7c00h
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129 <1> push di
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130 <1> repe cmpsb
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131 <1> pop di
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132 <1> mov ax, [es:di+1ah] ; get cluster number from directory entry
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133 <1> clc
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134 <1> je ffDone
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135 <1>
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136 <1> add di, 20h ; go to next directory entry
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137 <1> cmp byte [es:di], 0 ; if the first byte of the name is 0,
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138 <1> jnz next_entry ; there is no more files in the directory
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139 <1>
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140 <1> stc
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141 <1> ffDone:
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142 <1> %endmacro
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143 <1>
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144 <1> ; GETDRIVEPARMS: Calculate start of some disk areas.
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145 <1>
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146 <1> %macro GETDRIVEPARMS 0
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147 <1> mov si, word nHidden
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148 <1> mov di, word nHidden_hi
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149 <1> add si, word resSectors
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150 <1> adc di, 0 ; DI:SI = first FAT sector
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151 <1>
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152 <1> mov word fat_start, si
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153 <1> mov word fat_start_hi, di
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154 <1>
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155 <1> mov al, nFats
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156 <1> xor ah, ah
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157 <1> mul word sectPerFat ; DX:AX = total number of FAT sectors
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158 <1>
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159 <1> add si, ax
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160 <1> adc di, dx ; DI:SI = first root directory sector
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161 <1> mov word root_dir_start, si
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162 <1> mov word root_dir_start_hi, di
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163 <1>
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164 <1> ; Calculate how many sectors the root directory occupies.
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165 <1> mov bx, bytesPerSector
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166 <1> mov cl, 5 ; divide BX by 32
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167 <1> shr bx, cl ; BX = directory entries per sector
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168 <1>
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169 <1> mov ax, nRootDir
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170 <1> xor dx, dx
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171 <1> div bx
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172 <1>
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173 <1> mov nRootDir, ax ; AX = sectors per root directory
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174 <1>
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175 <1> add si, ax
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176 <1> adc di, 0 ; DI:SI = first data sector
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177 <1>
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178 <1> mov data_start, si
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179 <1> mov data_start_hi, di
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180 <1> %endmacro
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181 <1>
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182 <1> ; GETFATCHAIN:
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183 <1> ;
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184 <1> ; Reads the FAT chain and stores it in a temporary buffer in the first
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185 <1> ; 64 kb. The FAT chain is stored an array of 16-bit cluster numbers,
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186 <1> ; ending with 0.
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187 <1> ;
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188 <1> ; The file must fit in conventional memory, so it can't be larger than
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189 <1> ; 640 kb. The sector size must be at least 512 bytes, so the FAT chain
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190 <1> ; can't be larger than around 3 kb.
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191 <1> ;
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192 <1> ; Call with: AX = first cluster in chain
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193 <1> ;
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194 <1> ; Returns: CF clear on success, set on error
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195 <1>
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196 <1> %macro GETFATCHAIN 0
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197 <1> push ax ; store first cluster number
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198 <1>
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199 <1> ; Load the complete FAT into memory. The FAT can't be larger
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200 <1> ; than 128 kb, so it should fit in the temporary buffer.
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201 <1>
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202 <1> mov es, tempbuf
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203 <1> xor bx, bx
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204 <1> mov di, sectPerFat
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205 <1> mov ax, word fat_start
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206 <1> mov dx, word fat_start_hi
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207 <1> call readDisk
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208 <1> pop ax ; restore first cluster number
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209 <1> jc boot_error
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210 <1>
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211 <1> ; Set ES:DI to the temporary storage for the FAT chain.
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212 <1> push ds
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213 <1> push es
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214 <1> pop ds
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215 <1> pop es
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216 <1> mov di, FATBUF
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217 <1>
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218 <1> next_clust: stosw ; store cluster number
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219 <1> mov si, ax ; SI = cluster number
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220 <1> cmp byte extBoot, 29h
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221 <1> jne fat_12
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222 <1> cmp byte [bp+filesys+4], '6' ; check for FAT-16 system
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223 <1> je fat_16
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224 <1>
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225 <1> ; This is a FAT-12 disk.
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226 <1>
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227 <1> fat_12: add si, si ; multiply cluster number by 3...
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228 <1> add si, ax
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229 <1> shr si, 1 ; ...and divide by 2
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230 <1> lodsw
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231 <1>
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232 <1> ; If the cluster number was even, the cluster value is now in
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233 <1> ; bits 0-11 of AX. If the cluster number was odd, the cluster
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234 <1> ; value is in bits 4-15, and must be shifted right 4 bits. If
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235 <1> ; the number was odd, CF was set in the last shift instruction.
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236 <1>
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237 <1> jnc fat_even
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238 <1> mov cl, 4
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239 <1> shr ax, cl ; shift the cluster number
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240 <1>
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241 <1> fat_even: and ah, 0fh ; mask off the highest 4 bits
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242 <1> cmp ax, 0fffh ; check for EOF
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243 <1> jmp short next_test
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244 <1>
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245 <1> ; This is a FAT-16 disk. The maximal size of a 16-bit FAT
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246 <1> ; is 128 kb, so it may not fit within a single 64 kb segment.
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247 <1>
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248 <1> fat_16: mov dx, tempbuf
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249 <1> add si, si ; multiply cluster number by two
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250 <1> jnc first_half ; if overflow...
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251 <1> add dh, 10h ; ...add 64 kb to segment value
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252 <1>
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253 <1> first_half: mov ds, dx ; DS:SI = pointer to next cluster
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254 <1> lodsw ; AX = next cluster
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255 <1>
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256 <1> cmp ax, 0fff8h ; >= FFF8 = 16-bit EOF
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257 <1> next_test: jb next_clust ; continue if not EOF
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258 <1>
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259 <1> finished: ; Mark end of FAT chain with 0, so we have a single
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260 <1> ; EOF marker for both FAT-12 and FAT-16 systems.
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261 <1>
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262 <1> xor ax, ax
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263 <1> stosw
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264 <1> fatError:
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265 <1> %endmacro
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266 <1>
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267 <1>
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268 <1> ; loadFile: Loads the file into memory, one cluster at a time.
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269 <1>
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270 <1> %macro LOADFILE 0
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271 <1> mov es, tempbuf ; set ES:BX to load address
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272 <1> xor bx, bx
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273 <1>
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274 <1> mov si, FATBUF ; set DS:SI to the FAT chain
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275 <1> push cs
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276 <1> pop ds
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277 <1>
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278 <1> next_cluster: lodsw ; AX = next cluster to read
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279 <1> or ax, ax ; if EOF...
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280 <1> je boot_success ; ...boot was successful
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281 <1>
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282 <1> dec ax ; cluster numbers start with 2
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283 <1> dec ax
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284 <1>
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285 <1> mov di, word sectPerCluster
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286 <1> and di, 0ffh ; DI = sectors per cluster
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287 <1> mul di
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288 <1> add ax, data_start
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289 <1> adc dx, data_start_hi ; DX:AX = first sector to read
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290 <1> call readDisk
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291 <1> jnc next_cluster
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292 <1>
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293 <1> %endmacro
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294
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295 ;
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296 ;
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297 ;
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298 00000003 00<rept> TIMES 3eh-($-$$) DB 0
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299
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300 %define tempbuf [bp+3eh]
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301 0000003E 0020 load_seg dw LOADSEG
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302
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303 00000040 FA real_start: cli
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304 00000041 FC cld
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305 00000042 8CC8 mov ax, cs
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306 00000044 8ED0 mov ss, ax ; initialize stack
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307 00000046 BD007C mov bp, 7c00h
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308 00000049 8D66E0 lea sp, [bp-20h]
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309 0000004C FB sti
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310
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311 0000004D 8EC0 mov es, ax
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312 0000004F 8ED8 mov ds, ax
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313 00000051 885624 mov drive, dl ; BIOS passes drive number in DL
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314
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315 GETDRIVEPARMS
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316 00000054 8B761C <1> mov si, word nHidden
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317 00000057 8B7E1E <1> mov di, word nHidden_hi
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318 0000005A 03760E <1> add si, word resSectors
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319 0000005D 81D70000 <1> adc di, 0
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320 <1>
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321 00000061 8976FC <1> mov word fat_start, si
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322 00000064 897EFE <1> mov word fat_start_hi, di
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323 <1>
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324 00000067 8A4610 <1> mov al, nFats
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325 0000006A 30E4 <1> xor ah, ah
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326 0000006C F76616 <1> mul word sectPerFat
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327 <1>
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328 0000006F 01C6 <1> add si, ax
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329 00000071 11D7 <1> adc di, dx
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330 00000073 8976F8 <1> mov word root_dir_start, si
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331 00000076 897EFA <1> mov word root_dir_start_hi, di
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332 <1>
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333 <1>
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334 00000079 8B5E0B <1> mov bx, bytesPerSector
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335 0000007C B105 <1> mov cl, 5
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336 0000007E D3EB <1> shr bx, cl
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337 <1>
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338 00000080 8B4611 <1> mov ax, nRootDir
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339 00000083 31D2 <1> xor dx, dx
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340 00000085 F7F3 <1> div bx
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341 <1>
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342 00000087 894611 <1> mov nRootDir, ax
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343 <1>
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||||||
344 0000008A 01C6 <1> add si, ax
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|
||||||
345 0000008C 81D70000 <1> adc di, 0
|
|
||||||
346 <1>
|
|
||||||
347 00000090 8976F4 <1> mov data_start, si
|
|
||||||
348 00000093 897EF6 <1> mov data_start_hi, di
|
|
||||||
349
|
|
||||||
350 FINDFILE ; locate file in root directory
|
|
||||||
351 <1>
|
|
||||||
352 <1>
|
|
||||||
353 <1>
|
|
||||||
354 00000096 8B46F8 <1> mov ax, word root_dir_start
|
|
||||||
355 00000099 8B56FA <1> mov dx, word root_dir_start_hi
|
|
||||||
356 0000009C 8B7E11 <1> mov di, nRootDir
|
|
||||||
357 0000009F 31DB <1> xor bx, bx
|
|
||||||
358 000000A1 8E463E <1> mov es, tempbuf
|
|
||||||
359 000000A4 E8B900 <1> call readDisk
|
|
||||||
360 000000A7 721E <1> jc ffDone
|
|
||||||
361 <1>
|
|
||||||
362 000000A9 31FF <1> xor di, di
|
|
||||||
363 <1>
|
|
||||||
364 000000AB B90B00 <1> next_entry: mov cx, 11
|
|
||||||
365 000000AE BE[F17D] <1> mov si, filename+7c00h
|
|
||||||
366 000000B1 57 <1> push di
|
|
||||||
367 000000B2 F3A6 <1> repe cmpsb
|
|
||||||
368 000000B4 5F <1> pop di
|
|
||||||
369 000000B5 268B451A <1> mov ax, [es:di+1ah]
|
|
||||||
370 000000B9 F8 <1> clc
|
|
||||||
371 000000BA 740B <1> je ffDone
|
|
||||||
372 <1>
|
|
||||||
373 000000BC 81C72000 <1> add di, 20h
|
|
||||||
374 000000C0 26803D00 <1> cmp byte [es:di], 0
|
|
||||||
375 000000C4 75E5 <1> jnz next_entry
|
|
||||||
376 <1>
|
|
||||||
377 000000C6 F9 <1> stc
|
|
||||||
378 <1> ffDone:
|
|
||||||
379 000000C7 727A jc boot_error ; fail if not found
|
|
||||||
380
|
|
||||||
381 GETFATCHAIN ; read FAT chain
|
|
||||||
382 000000C9 50 <1> push ax
|
|
||||||
383 <1>
|
|
||||||
384 <1>
|
|
||||||
385 <1>
|
|
||||||
386 <1>
|
|
||||||
387 000000CA 8E463E <1> mov es, tempbuf
|
|
||||||
388 000000CD 31DB <1> xor bx, bx
|
|
||||||
389 000000CF 8B7E16 <1> mov di, sectPerFat
|
|
||||||
390 000000D2 8B46FC <1> mov ax, word fat_start
|
|
||||||
391 000000D5 8B56FE <1> mov dx, word fat_start_hi
|
|
||||||
392 000000D8 E88500 <1> call readDisk
|
|
||||||
393 000000DB 58 <1> pop ax
|
|
||||||
394 000000DC 7265 <1> jc boot_error
|
|
||||||
395 <1>
|
|
||||||
396 <1>
|
|
||||||
397 000000DE 1E <1> push ds
|
|
||||||
398 000000DF 06 <1> push es
|
|
||||||
399 000000E0 1F <1> pop ds
|
|
||||||
400 000000E1 07 <1> pop es
|
|
||||||
401 000000E2 BF0040 <1> mov di, FATBUF
|
|
||||||
402 <1>
|
|
||||||
403 000000E5 AB <1> next_clust: stosw
|
|
||||||
404 000000E6 89C6 <1> mov si, ax
|
|
||||||
405 000000E8 807E2629 <1> cmp byte extBoot, 29h
|
|
||||||
406 000000EC 7506 <1> jne fat_12
|
|
||||||
407 000000EE 807E3A36 <1> cmp byte [bp+filesys+4], '6'
|
|
||||||
408 000000F2 7415 <1> je fat_16
|
|
||||||
409 <1>
|
|
||||||
410 <1>
|
|
||||||
411 <1>
|
|
||||||
412 000000F4 01F6 <1> fat_12: add si, si
|
|
||||||
413 000000F6 01C6 <1> add si, ax
|
|
||||||
414 000000F8 D1EE <1> shr si, 1
|
|
||||||
415 000000FA AD <1> lodsw
|
|
||||||
416 <1>
|
|
||||||
417 <1>
|
|
||||||
418 <1>
|
|
||||||
419 <1>
|
|
||||||
420 <1>
|
|
||||||
421 <1>
|
|
||||||
422 000000FB 7304 <1> jnc fat_even
|
|
||||||
423 000000FD B104 <1> mov cl, 4
|
|
||||||
424 000000FF D3E8 <1> shr ax, cl
|
|
||||||
425 <1>
|
|
||||||
426 00000101 80E40F <1> fat_even: and ah, 0fh
|
|
||||||
427 00000104 3DFF0F <1> cmp ax, 0fffh
|
|
||||||
428 00000107 EB10 <1> jmp short next_test
|
|
||||||
429 <1>
|
|
||||||
430 <1>
|
|
||||||
431 <1>
|
|
||||||
432 <1>
|
|
||||||
433 00000109 8B563E <1> fat_16: mov dx, tempbuf
|
|
||||||
434 0000010C 01F6 <1> add si, si
|
|
||||||
435 0000010E 7303 <1> jnc first_half
|
|
||||||
436 00000110 80C610 <1> add dh, 10h
|
|
||||||
437 <1>
|
|
||||||
438 00000113 8EDA <1> first_half: mov ds, dx
|
|
||||||
439 00000115 AD <1> lodsw
|
|
||||||
440 <1>
|
|
||||||
441 00000116 3DF8FF <1> cmp ax, 0fff8h
|
|
||||||
442 00000119 72CA <1> next_test: jb next_clust
|
|
||||||
443 <1>
|
|
||||||
444 <1> finished:
|
|
||||||
445 <1>
|
|
||||||
446 <1>
|
|
||||||
447 0000011B 31C0 <1> xor ax, ax
|
|
||||||
448 0000011D AB <1> stosw
|
|
||||||
449 <1> fatError:
|
|
||||||
450 LOADFILE ; load file (jumps to boot_sucess if successful)
|
|
||||||
451 0000011E 8E463E <1> mov es, tempbuf
|
|
||||||
452 00000121 31DB <1> xor bx, bx
|
|
||||||
453 <1>
|
|
||||||
454 00000123 BE0040 <1> mov si, FATBUF
|
|
||||||
455 00000126 0E <1> push cs
|
|
||||||
456 00000127 1F <1> pop ds
|
|
||||||
457 <1>
|
|
||||||
458 00000128 AD <1> next_cluster: lodsw
|
|
||||||
459 00000129 09C0 <1> or ax, ax
|
|
||||||
460 0000012B 742B <1> je boot_success
|
|
||||||
461 <1>
|
|
||||||
462 0000012D 48 <1> dec ax
|
|
||||||
463 0000012E 48 <1> dec ax
|
|
||||||
464 <1>
|
|
||||||
465 0000012F 8B7E0D <1> mov di, word sectPerCluster
|
|
||||||
466 00000132 81E7FF00 <1> and di, 0ffh
|
|
||||||
467 00000136 F7E7 <1> mul di
|
|
||||||
468 00000138 0346F4 <1> add ax, data_start
|
|
||||||
469 0000013B 1356F6 <1> adc dx, data_start_hi
|
|
||||||
470 0000013E E81F00 <1> call readDisk
|
|
||||||
471 00000141 73E5 <1> jnc next_cluster
|
|
||||||
472 <1>
|
|
||||||
473
|
|
||||||
474 00000143 B90A00 boot_error: mov cx, ERRMSGLEN
|
|
||||||
475 00000146 BE[E77D] mov si, errmsg+7c00h
|
|
||||||
476
|
|
||||||
477 00000149 AC next_char: lodsb ; print error message
|
|
||||||
478 0000014A B40E mov ah, 0eh
|
|
||||||
479 0000014C 30FF xor bh, bh
|
|
||||||
480 0000014E CD10 int 10h
|
|
||||||
481 00000150 E2F7 loop next_char
|
|
||||||
482
|
|
||||||
483 00000152 30E4 xor ah, ah
|
|
||||||
484 00000154 CD16 int 16h ; wait for keystroke
|
|
||||||
485 00000156 CD19 int 19h ; invoke bootstrap loader
|
|
||||||
486
|
|
||||||
487 00000158 8A5624 boot_success: mov dl, drive
|
|
||||||
488
|
|
||||||
489 0000015B EA db 0eah ; far jump to LOADSEG:0000
|
|
||||||
490 0000015C 0000 dw 0
|
|
||||||
491 0000015E 0020 dw LOADSEG
|
|
||||||
492
|
|
||||||
493
|
|
||||||
494 ; readDisk: Reads a number of sectors into memory.
|
|
||||||
495 ;
|
|
||||||
496 ; Call with: DX:AX = 32-bit DOS sector number
|
|
||||||
497 ; DI = number of sectors to read
|
|
||||||
498 ; ES:BX = destination buffer
|
|
||||||
499 ; ES must be 64k aligned (1000h, 2000h etc).
|
|
||||||
500 ;
|
|
||||||
501 ; Returns: CF set on error
|
|
||||||
502 ; ES:BX points one byte after the last byte read.
|
|
||||||
503
|
|
||||||
504 readDisk:
|
|
||||||
505 00000160 56 push si
|
|
||||||
506 00000161 52 read_next: push dx
|
|
||||||
507 00000162 50 push ax
|
|
||||||
508
|
|
||||||
509 ;
|
|
||||||
510 ; translate sector number to BIOS parameters
|
|
||||||
511 ;
|
|
||||||
512
|
|
||||||
513 ;
|
|
||||||
514 ; abs = sector offset in track
|
|
||||||
515 ; + head * sectPerTrack offset in cylinder
|
|
||||||
516 ; + track * sectPerTrack * nHeads offset in platter
|
|
||||||
517 ;
|
|
||||||
518 ; t1 = abs / sectPerTrack (ax has t1)
|
|
||||||
519 ; sector = abs mod sectPerTrack (cx has sector)
|
|
||||||
520 ;
|
|
||||||
521 00000163 F77618 div word sectPerTrack
|
|
||||||
522 00000166 89D1 mov cx, dx
|
|
||||||
523
|
|
||||||
524 ;
|
|
||||||
525 ; t1 = head + track * nHeads
|
|
||||||
526 ;
|
|
||||||
527 ; track = t1 / nHeads (ax has track)
|
|
||||||
528 ; head = t1 mod nHeads (dl has head)
|
|
||||||
529 ;
|
|
||||||
530 00000168 31D2 xor dx, dx
|
|
||||||
531 0000016A F7761A div word nHeads
|
|
||||||
532
|
|
||||||
533 ; the following manipulations are necessary in order to
|
|
||||||
534 ; properly place parameters into registers.
|
|
||||||
535 ; ch = cylinder number low 8 bits
|
|
||||||
536 ; cl = 7-6: cylinder high two bits
|
|
||||||
537 ; 5-0: sector
|
|
||||||
538 0000016D 88D6 mov dh, dl ; save head into dh for bios
|
|
||||||
539 0000016F D0CC ror ah, 1 ; move track high bits into
|
|
||||||
540 00000171 D0CC ror ah, 1 ; bits 7-6 (assumes top = 0)
|
|
||||||
541 00000173 86C4 xchg al, ah ; swap for later
|
|
||||||
542 00000175 8A5618 mov dl, byte sectPerTrack
|
|
||||||
543 00000178 28CA sub dl, cl
|
|
||||||
544 0000017A FEC1 inc cl ; sector offset from 1
|
|
||||||
545 0000017C 09C1 or cx, ax ; merge cylinder into sector
|
|
||||||
546 0000017E 88D0 mov al, dl ; al has # of sectors left
|
|
||||||
547
|
|
||||||
548 ; Calculate how many sectors can be transfered in this read
|
|
||||||
549 ; due to dma boundary conditions.
|
|
||||||
550 00000180 52 push dx
|
|
||||||
551
|
|
||||||
552 00000181 89FE mov si, di ; temp register save
|
|
||||||
553 ; this computes remaining bytes because of modulo 65536
|
|
||||||
554 ; nature of dma boundary condition
|
|
||||||
555 00000183 89D8 mov ax, bx ; get offset pointer
|
|
||||||
556 00000185 F7D8 neg ax ; and convert to bytes
|
|
||||||
557 00000187 740B jz ax_min_1 ; started at seg:0, skip ahead
|
|
||||||
558
|
|
||||||
559 00000189 31D2 xor dx, dx ; convert to sectors
|
|
||||||
560 0000018B F7760B div word bytesPerSector
|
|
||||||
561
|
|
||||||
562 0000018E 39F8 cmp ax, di ; check remainder vs. asked
|
|
||||||
563 00000190 7202 jb ax_min_1 ; less, skip ahead
|
|
||||||
564 00000192 89C6 mov si, ax ; transfer only what we can
|
|
||||||
565
|
|
||||||
566 00000194 5A ax_min_1: pop dx
|
|
||||||
567
|
|
||||||
568 ; Check that request sectors do not exceed track boundary
|
|
||||||
569 00000195 8B7618 mov si, sectPerTrack
|
|
||||||
570 00000198 46 inc si
|
|
||||||
571 00000199 89C8 mov ax, cx ; get the sector/cyl byte
|
|
||||||
572 0000019B 253F00 and ax, 03fh ; and mask out sector
|
|
||||||
573 0000019E 29C6 sub si, ax ; si has how many we can read
|
|
||||||
574 000001A0 89F8 mov ax, di
|
|
||||||
575 000001A2 39FE cmp si, di ; see if asked <= available
|
|
||||||
576 000001A4 7D02 jge ax_min_2
|
|
||||||
577 000001A6 89F0 mov ax, si ; get what can be xfered
|
|
||||||
578
|
|
||||||
579 000001A8 BE0500 ax_min_2: mov si, RETRYCOUNT
|
|
||||||
580 000001AB B402 mov ah, 2
|
|
||||||
581 000001AD 8A5624 mov dl, drive
|
|
||||||
582
|
|
||||||
583 000001B0 50 retry: push ax
|
|
||||||
584 000001B1 CD13 int 13h
|
|
||||||
585 000001B3 58 pop ax
|
|
||||||
586 000001B4 7310 jnc read_ok
|
|
||||||
587 000001B6 50 push ax
|
|
||||||
588 000001B7 31C0 xor ax, ax ; reset the drive
|
|
||||||
589 000001B9 CD13 int 13h
|
|
||||||
590 000001BB 58 pop ax
|
|
||||||
591 000001BC 4E dec si
|
|
||||||
592 000001BD 75F1 jnz retry
|
|
||||||
593 000001BF F9 stc
|
|
||||||
594 000001C0 58 pop ax
|
|
||||||
595 000001C1 5A pop dx
|
|
||||||
596 000001C2 5E pop si
|
|
||||||
597 000001C3 C3 ret
|
|
||||||
598
|
|
||||||
599 000001C4 EB9B read_next_jmp: jmp short read_next
|
|
||||||
600 000001C6 30E4 read_ok: xor ah, ah
|
|
||||||
601 000001C8 89C6 mov si, ax ; AX = SI = number of sectors read
|
|
||||||
602 000001CA F7660B mul word bytesPerSector ; AX = number of bytes read
|
|
||||||
603 000001CD 01C3 add bx, ax ; add number of bytes read to BX
|
|
||||||
604 000001CF 7307 jnc no_incr_es ; if overflow...
|
|
||||||
605
|
|
||||||
606 000001D1 8CC0 mov ax, es
|
|
||||||
607 000001D3 80C410 add ah, 10h ; ...add 1000h to ES
|
|
||||||
608 000001D6 8EC0 mov es, ax
|
|
||||||
609
|
|
||||||
610 000001D8 58 no_incr_es: pop ax
|
|
||||||
611 000001D9 5A pop dx ; DX:AX = last sector number
|
|
||||||
612
|
|
||||||
613 000001DA 01F0 add ax, si
|
|
||||||
614 000001DC 81D20000 adc dx, 0 ; DX:AX = next sector to read
|
|
||||||
615 000001E0 29F7 sub di, si ; if there is anything left to read,
|
|
||||||
616 000001E2 7FE0 jg read_next_jmp ; continue
|
|
||||||
617
|
|
||||||
618 000001E4 F8 clc
|
|
||||||
619 000001E5 5E pop si
|
|
||||||
620 000001E6 C3 ret
|
|
||||||
621
|
|
||||||
622 000001E7 426F6F74206572726F- errmsg db "Boot error"
|
|
||||||
623 000001F0 72
|
|
||||||
624 ERRMSGLEN equ $ - errmsg
|
|
||||||
625
|
|
||||||
626
|
|
||||||
627 ;filename db "OSLDR BIN"
|
|
||||||
628 000001F1 4B45524E454C202042- filename db "KERNEL BIN"
|
|
||||||
629 000001FA 494E
|
|
||||||
630
|
|
||||||
631 000001FC 00<rept> TIMES 510-($-$$) DB 0
|
|
||||||
632 000001FE 55AA sign dw 0aa55h
|
|
||||||
633
|
|
||||||
634
|
|
||||||
635
|
|
||||||
636
|
|
||||||
637
|
|
||||||
Loading…
Reference in a new issue