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Rev | Author | Line No. | Line |
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796 | shurf | 1 | ; FAT12 boot sector for Kolibri OS |
2 | ; |
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3 | ; Copyright (C) Alex Nogueira Teixeira |
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4 | ; Copyright (C) Diamond |
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5 | ; Copyright (C) Dmitry Kartashov aka shurf |
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6 | ; |
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7 | ; Distributed under GPL, see file COPYING for details |
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8 | ; |
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9 | ; Version 1.0 |
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10 | |||
11 | lf equ 0ah |
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12 | cr equ 0dh |
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13 | |||
14 | pos_read_tmp equ 0700h ;position for temporary read |
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15 | boot_program equ 07c00h ;position for boot code |
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16 | seg_read_kernel equ 01000h ;segment to kernel read |
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17 | |||
18 | jmp start_program |
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19 | nop |
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20 | |||
21 | ; Boot Sector and BPB Structure |
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22 | include 'floppy1440.inc' |
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23 | ;include 'floppy2880.inc' |
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24 | |||
25 | start_program: |
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26 | |||
27 | xor ax,ax |
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28 | mov ss,ax |
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29 | mov sp,boot_program |
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30 | push ss |
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31 | pop ds |
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32 | |||
33 | ; print loading string |
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34 | mov si,loading+boot_program |
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35 | loop_loading: |
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36 | lodsb |
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37 | or al,al |
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38 | jz read_root_directory |
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39 | mov ah,0eh |
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40 | mov bx,7 |
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41 | int 10h |
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42 | jmp loop_loading |
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43 | |||
44 | read_root_directory: |
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45 | push ss |
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46 | pop es |
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47 | |||
48 | ; reading root directory |
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1940 | art_zh | 49 | ; al=count root dir sectors !!!! TODO: al, max 255 sectors !!!! |
796 | shurf | 50 | mov ah,2 ; read |
51 | push ax |
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52 | |||
53 | mov ax,word [FirstRootDirSecNum+boot_program] |
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54 | call conv_abs_to_THS ; convert abs sector (AX) to BIOS T:H:S (track:head:sector) |
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55 | pop ax |
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56 | mov bx,pos_read_tmp ; es:bx read buffer |
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57 | call read_sector |
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58 | |||
59 | mov si,bx ; read buffer address: es:si |
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60 | mov ax,[RootDirSecs+boot_program] |
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61 | mul word [BPB_BytsPerSec+boot_program] |
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62 | add ax,si ; AX = end of root dir. in buffer pos_read_tmp |
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63 | |||
64 | ; find kernel file in root directory |
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65 | loop_find_dir_entry: |
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66 | push si |
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67 | mov cx,11 |
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68 | mov di,kernel_name+boot_program |
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69 | rep cmpsb ; compare es:si and es:di, cx bytes long |
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70 | pop si |
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71 | je found_kernel_file |
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72 | add si,32 ; next dir. entry |
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73 | cmp si,ax ; end of directory |
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74 | jb loop_find_dir_entry |
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1940 | art_zh | 75 | jmp $ |
796 | shurf | 76 | |
77 | ; === KERNEL FOUND. LOADING... === |
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78 | |||
79 | found_kernel_file: |
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80 | mov bp,[si+01ah] ; first cluster of kernel file |
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81 | ; |
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82 | mov [cluster1st+boot_program],bp ; starting cluster of kernel file |
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83 | ; <\diamond> |
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84 | |||
85 | ; reading first FAT table |
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86 | mov ax,word [BPB_RsvdSecCnt+boot_program] ; begin first FAT abs sector number |
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87 | call conv_abs_to_THS ; convert abs sector (AX) to BIOS T:H:S (track:head:sector) |
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88 | mov bx,pos_read_tmp ; es:bx read position |
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89 | mov ah,2 ; ah=2 (read) |
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90 | mov al, byte [BPB_FATSz16+boot_program] ; FAT size in sectors (TODO: max 255 sectors) |
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91 | call read_sector |
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92 | |||
93 | mov ax,seg_read_kernel |
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94 | mov es,ax |
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1940 | art_zh | 95 | xor bx,bx ; es:bx = 1000h:0000h |
796 | shurf | 96 | |
97 | ; reading kernel file |
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98 | loop_obtains_kernel_data: |
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1940 | art_zh | 99 | call obtain_cluster ; read one cluster of file |
796 | shurf | 100 | |
1940 | art_zh | 101 | mov ax,es |
102 | add ax,seg_inc_per_cluster ; << =32(1.44M) or 64(2.88) >> |
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103 | mov es,ax ; add one cluster length to segment:offset |
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796 | shurf | 104 | |
105 | mov di,bp |
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106 | shr di,1 |
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107 | pushf |
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108 | add di,bp ; di = bp * 1.5 |
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109 | add di,pos_read_tmp |
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110 | mov ax,[di] ; read next entry from FAT-chain |
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111 | popf |
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112 | jc move_4_right |
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113 | and ax,0fffh |
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114 | jmp verify_end_sector |
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115 | move_4_right: |
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1940 | art_zh | 116 | shr ax,4 |
796 | shurf | 117 | verify_end_sector: |
118 | cmp ax,0ff8h ; last cluster |
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119 | jae execute_kernel |
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120 | mov bp,ax |
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121 | jmp loop_obtains_kernel_data |
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122 | |||
123 | execute_kernel: |
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124 | ; |
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125 | mov ax,'KL' |
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126 | push 0 |
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127 | pop ds |
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128 | mov si,loader_block+boot_program |
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129 | ; |
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130 | push word seg_read_kernel |
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131 | push word 0 |
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132 | retf ; jmp far 1000:0000 |
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133 | |||
134 | |||
135 | ;------------------------------------------ |
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136 | ; loading cluster from file to es:bx |
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137 | obtain_cluster: |
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138 | ; bp - cluster number to read |
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139 | ; carry = 0 -> read OK |
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140 | ; carry = 1 -> read ERROR |
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141 | |||
142 | ; print one dot |
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143 | push bx |
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144 | mov ax,0e2eh ; ah=0eh (teletype), al='.' |
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145 | xor bh,bh |
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1940 | art_zh | 146 | int 10h |
147 | ; jc $ ; error |
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148 | pop bx |
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796 | shurf | 149 | |
1940 | art_zh | 150 | writesec: |
796 | shurf | 151 | ; convert cluster number to sector number |
152 | mov ax,bp ; data cluster to read |
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153 | sub ax,2 |
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1940 | art_zh | 154 | ;>> add ax,ax ; << only for 2.88M disks! >> |
155 | add ax,word [data_start+boot_program] |
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796 | shurf | 156 | call conv_abs_to_THS ; convert abs sector (AX) to BIOS T:H:S (track:head:sector) |
1940 | art_zh | 157 | |
796 | shurf | 158 | patchhere: |
1940 | art_zh | 159 | mov ax,0x201 ; ah=2 (read) |
160 | ;>> ; al=1(1.44) or 2(2.88) |
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796 | shurf | 161 | ; read sector from disk |
1940 | art_zh | 162 | |
796 | shurf | 163 | read_sector: |
164 | push ax bx cx dx |
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165 | int 13h |
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1940 | art_zh | 166 | jc $ ; error: stop here |
796 | shurf | 167 | pop dx cx bx ax |
168 | retn |
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1940 | art_zh | 169 | |
796 | shurf | 170 | ;------------------------------------------ |
1940 | art_zh | 171 | ; converts abs. sector number (AX) to BIOS T:H:S |
172 | ; Returns: {pre.track number = (AX / BPB_SecPerTrk)} |
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173 | ; ch - track number = pre.track number/2 |
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174 | ; cl - sector number = (abs.sector%BPB_SecPerTrk)+1 |
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175 | ; dh - head number = pre.track number%BPB_NumHeads |
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176 | ; dl - drive number (0 = a:) |
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796 | shurf | 177 | conv_abs_to_THS: |
1940 | art_zh | 178 | mov cx,word [BPB_SecPerTrk+boot_program] ; << 18 or 36 >> |
796 | shurf | 179 | xor dx,dx |
1940 | art_zh | 180 | div cx |
796 | shurf | 181 | inc dx |
1940 | art_zh | 182 | mov cl, dl ; cl = sector number |
183 | xor dx, dx |
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184 | shr ax, 1 |
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185 | rol dx, 1 ; dh = head number |
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186 | mov ch, al ; ch = track number |
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796 | shurf | 187 | retn |
188 | ;------------------------------------------ |
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189 | |||
190 | loading db cr,lf,'Starting system ',00h |
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1940 | art_zh | 191 | ;error_message db 13,10 |
192 | kernel_name db 'KERNEL MNT',00h |
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193 | FirstRootDirSecNum dw 19 ; 1st sector of the root dir |
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194 | RootDirSecs dw 14 ; << = 14(1.44M) or 15(2.88M) >> |
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195 | data_start dw 33 ; << = 33(1.44M) or 34(2.88M) >> |
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796 | shurf | 196 | |
197 | ; |
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198 | write1st: |
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199 | push cs |
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200 | pop ds |
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201 | mov byte [patchhere+1+boot_program], 3 ; change ah=2 to ah=3 |
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1940 | art_zh | 202 | mov bp,[cluster1st+boot_program] |
796 | shurf | 203 | push 1000h |
204 | pop es |
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205 | xor bx,bx |
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206 | call writesec |
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207 | mov byte [patchhere+1+boot_program], 2 ; change back ah=3 to ah=2 |
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208 | retf |
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1940 | art_zh | 209 | |
210 | cluster1st dw ? ; 1st cluster of kernel.mnt |
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796 | shurf | 211 | loader_block: |
212 | db 1 |
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213 | dw 0 |
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214 | dw write1st+boot_program |
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215 | dw 0 |
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216 | ; <\diamond> |
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1940 | art_zh | 217 | |
796 | shurf | 218 | times 0x1fe-$ db 00h |
219 | |||
220 | db 55h,0aah ;boot signature\diamond>><>><>><>><>><>\diamond> |