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Rev | Author | Line No. | Line |
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2783 | clevermous | 1 | ; KolibriOS bootloader |
2 | ; bootsector for loading from FAT32 flash (or hard) drive |
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3 | ; intended for use with mtldr_f file in root folder |
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4 | ; this code has been written by diamond in 2005,2006,2007 specially for KolibriOS |
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5 | |||
6 | ; this code is loaded by BIOS to 0000:7C00 |
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7 | org 0x7C00 |
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8 | jmp @f |
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9 | nop |
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2785 | clevermous | 10 | times 57h db 0 |
11 | ; file 'bt2.dat':3,57h |
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2783 | clevermous | 12 | @@: |
4299 | clevermous | 13 | cmp byte [si], 80h |
14 | jnz @f |
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15 | mov eax, [si+8] |
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16 | mov [cs:7C1Ch], eax |
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17 | @@: |
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2783 | clevermous | 18 | xor eax, eax |
19 | mov ds, ax |
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20 | mov ss, ax |
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21 | mov sp, 7C00h |
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4299 | clevermous | 22 | mov bp, sp |
2783 | clevermous | 23 | mov [boot_drive], dl |
24 | cld |
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25 | sti |
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26 | push 800h |
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27 | pop es |
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4299 | clevermous | 28 | movzx ebx, word [bp+0Eh] ; reserved_sect |
2783 | clevermous | 29 | mov [fat_start], ebx |
4299 | clevermous | 30 | mov al, byte [bp+10h] ; num_fats |
31 | mul dword [bp+24h] ; sect_fat |
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2783 | clevermous | 32 | add eax, ebx |
33 | ; cluster 2 begins from sector eax |
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4299 | clevermous | 34 | movzx ebx, byte [bp+0Dh] ; sects_per_clust |
2783 | clevermous | 35 | add bx, bx |
36 | sub eax, ebx |
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37 | mov [data_start], eax |
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4299 | clevermous | 38 | mov eax, [bp+2Ch] ; root_cluster |
2783 | clevermous | 39 | and eax, 0FFFFFFFh |
40 | fat32_parse_dir: |
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41 | xor bx, bx |
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42 | mov di, bx |
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43 | push eax |
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44 | call read_cluster |
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4299 | clevermous | 45 | movzx cx, byte [bp+0Dh] ; sects_per_clust |
2783 | clevermous | 46 | shl cx, 4 ; *0x200/0x20 |
47 | scan_cluster: |
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48 | cmp byte [es:di], 0 |
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49 | jz file_not_found |
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50 | push cx di |
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51 | mov cx, 11 |
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52 | mov si, mtldr_f |
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53 | repz cmpsb |
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54 | pop di cx |
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55 | jz file_found |
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56 | add di, 20h |
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57 | loop scan_cluster |
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58 | pop eax |
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59 | call next_cluster |
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60 | jnc file_not_found |
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61 | jc fat32_parse_dir |
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62 | file_found: |
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63 | pop eax |
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64 | mov ax, [es:di+14h] |
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65 | and ax, 0FFFh |
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66 | shl eax, 10h |
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67 | mov ax, [es:di+1Ah] |
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68 | ; eax contains first cluster |
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69 | @@: |
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70 | xor bx, bx |
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71 | push eax |
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72 | call read_cluster |
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73 | mov ax, es |
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4299 | clevermous | 74 | movzx cx, byte [bp+0Dh] |
2783 | clevermous | 75 | shl cx, 5 |
76 | add ax, cx |
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77 | mov es, ax |
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78 | pop eax |
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79 | call next_cluster |
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80 | jc @b |
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81 | jmp 0:8000h |
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82 | |||
83 | file_not_found: |
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84 | mov si, file_not_found_msg |
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85 | sayerr: |
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86 | call out_string |
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87 | jmp $ |
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88 | |||
89 | read_cluster: |
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90 | ; in: eax = cluster, bx->buffer |
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4299 | clevermous | 91 | movzx ecx, byte [bp+0Dh] |
2783 | clevermous | 92 | mul ecx |
93 | add eax, [data_start] |
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94 | |||
95 | ; read procedure |
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96 | ; in: eax = absolute sector |
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97 | ; cx = number of sectors |
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98 | ; es:bx -> buffer |
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99 | read: |
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4299 | clevermous | 100 | add eax, [bp+1Ch] ; hidden sectors |
2783 | clevermous | 101 | push es |
102 | read_loop: |
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103 | pushad |
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104 | ; allocate disk address packet on the stack |
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105 | ; qword +8: absolute block number |
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106 | push 0 |
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107 | push 0 ; dword +C is high dword |
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108 | push eax ; dword +8 is low dword |
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109 | ; dword +4: buffer address |
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110 | push es ; word +6 is segment |
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111 | push bx ; word +4 is offset |
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112 | ; word +2: number of blocks, limited to 7Fh |
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113 | sub cx, 7Fh |
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114 | sbb ax, ax |
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115 | and ax, cx |
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116 | add ax, 7Fh |
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117 | push ax |
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118 | shl ax, 5 |
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119 | mov cx, es |
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120 | add cx, ax |
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121 | mov es, cx |
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122 | ; word +0: size of packet = 10h |
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123 | push 10h |
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124 | ; now pair ss:sp contain address of disk address packet |
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125 | mov ax, 4200h |
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126 | mov dl, [boot_drive] |
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127 | mov si, sp |
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128 | int 13h |
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129 | mov si, disk_read_err |
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130 | jc sayerr |
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131 | popaw |
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132 | popad |
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133 | add eax, 7Fh |
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134 | sub cx, 7Fh |
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135 | ja read_loop |
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136 | pop es |
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137 | ret |
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138 | |||
139 | next_cluster: |
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140 | push es |
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141 | push ds |
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142 | pop es |
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143 | mov bx, 7E00h |
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144 | ; sector is 200h bytes long, one entry in FAT occupies 4 bytes |
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145 | ; => 80h entries in sector |
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146 | push eax |
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147 | shr eax, 7 ; div 80h |
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148 | cmp eax, [fat_cur_sector] |
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149 | jz @f |
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150 | mov [fat_cur_sector], eax |
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151 | add eax, [fat_start] |
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152 | mov cx, 1 |
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153 | call read |
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154 | @@: |
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155 | pop eax |
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156 | and eax, 7Fh |
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157 | mov eax, [7E00h+eax*4] |
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158 | and eax, 0FFFFFFFh |
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159 | cmp eax, 0FFFFFF7h |
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160 | mov si, bad_cluster |
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161 | jz sayerr |
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162 | pop es |
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163 | ret |
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164 | |||
165 | out_string: |
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166 | lodsb |
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167 | test al, al |
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168 | jz .xxx |
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169 | mov ah, 0Eh |
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170 | mov bx, 7 |
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171 | int 10h |
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172 | jmp out_string |
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173 | .xxx: ret |
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174 | |||
175 | file_not_found_msg db 'Cannot find file ' |
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176 | mtldr_f db 'MTLD_F32 ' |
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177 | db 13,10,0 |
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178 | disk_read_err db 'Disk read error',13,10,0 |
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179 | bad_cluster db 'Bad cluster',13,10,0 |
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180 | fat_cur_sector dd -1 |
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181 | |||
182 | times (7DFEh - $) db 0 |
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183 | db 55h, 0AAh |
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184 | |||
185 | virtual at 7A00h |
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186 | fat_start dd ? |
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187 | data_start dd ? |
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188 | boot_drive db ? |
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189 | end virtual |