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pascal@24476
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1 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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2 ;; ;;
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pascal@24476
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3 ;; "BootProg" Loader v 1.5 by Alexey Frunze (c) 2000-2015 ;;
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pascal@24476
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4 ;; 2-clause BSD license. ;;
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pascal@24476
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5 ;; ;;
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pascal@24476
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6 ;; ;;
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pascal@24476
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7 ;; How to Compile: ;;
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pascal@24476
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8 ;; ~~~~~~~~~~~~~~~ ;;
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pascal@24476
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9 ;; nasm boot16.asm -f bin -o boot16.bin ;;
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pascal@24476
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10 ;; ;;
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pascal@24476
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11 ;; ;;
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pascal@24476
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12 ;; Features: ;;
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pascal@24476
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13 ;; ~~~~~~~~~ ;;
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pascal@24476
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14 ;; - FAT12 and FAT16 supported using BIOS int 13h function 42h or 02h. ;;
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pascal@24476
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15 ;; ;;
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pascal@24476
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16 ;; - Loads a 16-bit executable file in the MS-DOS .COM or .EXE format ;;
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pascal@24476
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17 ;; from the root directory of a disk and transfers control to it ;;
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pascal@24476
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18 ;; (the "ProgramName" variable holds the name of the file to be loaded) ;;
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pascal@24476
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19 ;; Its maximum size can be up to 635KB without Extended BIOS Data area. ;;
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pascal@24476
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20 ;; ;;
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pascal@24476
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21 ;; - Prints an error if the file isn't found or couldn't be read ;;
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pascal@24476
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22 ;; ("File not found" or "Read error") ;;
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pascal@24476
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23 ;; and waits for a key to be pressed, then executes the Int 19h ;;
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pascal@24476
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24 ;; instruction and lets the BIOS continue bootstrap. ;;
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pascal@24476
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25 ;; ;;
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pascal@24476
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26 ;; - cpu 8086 is supported ;;
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pascal@24476
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27 ;; ;;
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pascal@24476
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28 ;; ;;
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pascal@24476
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29 ;; Known Limitations: ;;
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pascal@24476
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30 ;; ~~~~~~~~~~~~~~~~~~ ;;
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pascal@24476
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31 ;; - Works only on the 1st MBR partition which must be a PRI DOS partition ;;
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pascal@24476
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32 ;; with FAT12 (File System ID: 1) and FAT16 (File System ID: 4, 6) ;;
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pascal@24476
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33 ;; ;;
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pascal@24476
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34 ;; ;;
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pascal@24476
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35 ;; Known Bugs: ;;
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pascal@24476
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36 ;; ~~~~~~~~~~~ ;;
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pascal@24476
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37 ;; - All bugs are fixed as far as I know. The boot sector has been tested ;;
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pascal@24476
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38 ;; on the following types of diskettes (FAT12): ;;
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pascal@24476
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39 ;; - 360KB 5"25 ;;
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pascal@24476
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40 ;; - 1.2MB 5"25 ;;
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pascal@24476
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41 ;; - 1.44MB 3"5 ;;
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pascal@24476
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42 ;; on my HDD (FAT16). ;;
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pascal@24476
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43 ;; ;;
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pascal@24476
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44 ;; ;;
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pascal@24476
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45 ;; Memory Layout: ;;
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pascal@24476
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46 ;; ~~~~~~~~~~~~~~ ;;
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pascal@24476
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47 ;; The diagram below shows the typical memory layout. The actual location ;;
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pascal@24476
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48 ;; of the boot sector and its stack may be lower than A0000H if the BIOS ;;
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pascal@24476
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49 ;; reserves memory for its Extended BIOS Data Area just below A0000H and ;;
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pascal@24476
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50 ;; reports less than 640 KB of RAM via its Int 12H function. ;;
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pascal@24476
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51 ;; ;;
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pascal@24476
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52 ;; physical address ;;
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pascal@24476
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53 ;; +------------------------+ 00000H ;;
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pascal@24476
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54 ;; | Interrupt Vector Table | ;;
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pascal@24476
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55 ;; +------------------------+ 00400H ;;
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pascal@24476
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56 ;; | BIOS Data Area | ;;
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pascal@24476
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57 ;; +------------------------+ 00500H ;;
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pascal@24476
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58 ;; | PrtScr Status / Unused | ;;
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pascal@24476
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59 ;; +------------------------+ 00600H ;;
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pascal@24476
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60 ;; | Loaded Image | ;;
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pascal@24476
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61 ;; +------------------------+ nnnnnH ;;
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pascal@24476
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62 ;; | Available Memory | ;;
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pascal@24476
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63 ;; +------------------------+ A0000H - 512 - 3KB ;;
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pascal@24476
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64 ;; | Boot Sector | ;;
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pascal@24476
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65 ;; +------------------------+ A0000H - 3KB ;;
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pascal@24476
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66 ;; | 3KB Boot Stack | ;;
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pascal@24476
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67 ;; +------------------------+ A0000H ;;
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pascal@24476
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68 ;; | Video RAM | ;;
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pascal@24476
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69 ;; ;;
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pascal@24476
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70 ;; ;;
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pascal@24476
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71 ;; Boot Image Startup (register values): ;;
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pascal@24476
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72 ;; ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ;;
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pascal@24476
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73 ;; dl = BIOS boot drive number (e.g. 0, 80H) ;;
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pascal@24476
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74 ;; cs:ip = program entry point ;;
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pascal@24476
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75 ;; ss:sp = program stack (don't confuse with boot sector's stack) ;;
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pascal@24476
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76 ;; COM program defaults: cs = ds = es = ss = 50h, sp = 0, ip = 100h ;;
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pascal@24476
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77 ;; EXE program defaults: ds = es = EXE data - 10h (fake MS-DOS psp), ;;
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pascal@24476
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78 ;; ax = 0ffffh (both FCB in the PSP don't have a valid drive identifier), ;;
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pascal@24476
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79 ;; cs:ip and ss:sp depends on EXE header ;;
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pascal@24476
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80 ;; Magic numbers: ;;
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pascal@24476
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81 ;; si = 16381 (prime number 2**14-3) ;;
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pascal@24476
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82 ;; di = 32749 (prime number 2**15-19) ;;
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pascal@24476
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83 ;; bp = 65521 (prime number 2**16-15) ;;
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pascal@24476
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84 ;; The magic numbers let the program know whether it has been loaded by ;;
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pascal@24476
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85 ;; this boot sector or by MS-DOS, which may be handy for universal, bare- ;;
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pascal@24476
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86 ;; metal and MS-DOS programs. ;;
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pascal@24476
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87 ;; ;;
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pascal@24476
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88 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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89
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pascal@24476
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90 %define bx(label) bx+label-boot
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pascal@24476
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91
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pascal@24476
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92 [BITS 16]
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pascal@24476
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93 [CPU 8086]
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pascal@24476
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94
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pascal@24476
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95 ? equ 0
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pascal@24476
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96 ImageLoadSeg equ 60h
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pascal@24476
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97 StackSize equ 3072 ; Stack + cluster list
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pascal@24476
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98
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pascal@24476
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99 [SECTION .text]
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pascal@24476
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100 [ORG 0]
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pascal@24476
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101
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pascal@24476
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102 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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103 ;; Boot sector starts here ;;
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pascal@24476
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104 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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105
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pascal@24476
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106 boot:
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pascal@24476
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107 jmp short start ; MS-DOS/Windows checks for this jump
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pascal@24476
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108 nop
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pascal@24476
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109 bsOemName DB "BootProg" ; 0x03
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pascal@24476
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110
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pascal@24476
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111 ;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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112 ;; BPB starts here ;;
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pascal@24476
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113 ;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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114
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pascal@24476
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115 bpbBytesPerSector DW ? ; 0x0B
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pascal@24476
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116 bpbSectorsPerCluster DB ? ; 0x0D
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pascal@24476
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117 bpbReservedSectors DW ? ; 0x0E
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pascal@24476
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118 bpbNumberOfFATs DB ? ; 0x10
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pascal@24476
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119 bpbRootEntries DW ? ; 0x11
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pascal@24476
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120 bpbTotalSectors DW ? ; 0x13
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pascal@24476
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121 bpbMedia DB ? ; 0x15
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pascal@24476
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122 bpbSectorsPerFAT DW ? ; 0x16
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pascal@24476
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123 bpbSectorsPerTrack DW ? ; 0x18
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pascal@24476
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124 bpbHeadsPerCylinder DW ? ; 0x1A
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pascal@24476
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125 bpbHiddenSectors DD ? ; 0x1C
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pascal@24476
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126 bpbTotalSectorsBig DD ? ; 0x20
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pascal@24476
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127
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pascal@24476
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128 ;;;;;;;;;;;;;;;;;;;
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pascal@24476
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129 ;; BPB ends here ;;
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pascal@24476
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130 ;;;;;;;;;;;;;;;;;;;
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pascal@24476
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131
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pascal@24476
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132 bsDriveNumber DB ? ; 0x24
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pascal@24476
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133 bsUnused DB ? ; 0x25
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pascal@24476
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134 bsExtBootSignature DB ? ; 0x26
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pascal@24476
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135 bsSerialNumber DD ? ; 0x27
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pascal@24476
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136 bsVolumeLabel DB "NO NAME " ; 0x2B
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pascal@24476
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137 bsFileSystem DB "FAT12 " ; 0x36
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pascal@24476
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138
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pascal@24476
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139 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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140 ;; Boot sector code starts here ;;
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pascal@24476
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141 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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142
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pascal@24476
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143 start:
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pascal@24476
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144 cld
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pascal@24476
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145
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pascal@24476
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146 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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147 ;; How much RAM is there? ;;
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pascal@24476
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148 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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149
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pascal@24476
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150 int 12h ; get conventional memory size (in KBs)
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pascal@24476
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151 mov cx, 106h
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pascal@24476
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152 shl ax, cl ; and convert it to 16-byte paragraphs
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pascal@24476
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153
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pascal@24476
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154 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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155 ;; Reserve memory for the boot sector and its stack ;;
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pascal@24476
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156 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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157
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pascal@24476
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158 sub ax, (512+StackSize) /16 ; reserve bytes for the code and the stack
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pascal@24476
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159 mov es, ax ; cs:0 = ds:0 = ss:0 -> top - 512 - StackSize
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pascal@24476
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160 mov ss, ax
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pascal@24476
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161 mov sp, 512+StackSize ; bytes 0-511 are reserved for the boot code
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pascal@24476
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162
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pascal@24476
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163 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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164 ;; Copy ourselves to top of memory ;;
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pascal@24476
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165 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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166
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pascal@24476
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167 mov si, 7C00h
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pascal@24476
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168 xor di, di
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pascal@24476
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169 mov ds, di
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pascal@24476
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170 mov [si], dx ; store BIOS boot drive number
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pascal@24476
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171 rep movsw ; move 512 bytes (+ 12)
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pascal@24476
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172
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pascal@24476
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173 ;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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174 ;; Jump to the copy ;;
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pascal@24476
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175 ;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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176
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pascal@24476
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177 push es
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pascal@24476
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178 mov cl, byte main
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pascal@24476
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179 push cx
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pascal@24476
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180 retf
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pascal@24476
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181
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pascal@24476
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182 main:
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pascal@24476
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183 %if ImageLoadSeg != main-boot
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pascal@24476
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184 %if ImageLoadSeg >= 100h
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pascal@24476
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185 mov cx, ImageLoadSeg
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pascal@24476
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186 %else
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pascal@24476
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187 mov cl, ImageLoadSeg
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pascal@24476
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188 %endif
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pascal@24476
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189 %endif
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pascal@24476
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190 push cx
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pascal@24476
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191
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pascal@24476
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192 ;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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193 ;; Get drive parameters ;;
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pascal@24476
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194 ;; Update heads count ;;
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pascal@24476
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195 ;; for current BIOS ;;
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pascal@24476
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196 ;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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197
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pascal@24476
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198 mov ah, 8
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pascal@24476
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199 int 13h ; may destroy SI,BP, and DS registers
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pascal@24476
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200 ; update AX,BL,CX,DX,DI, and ES registers
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pascal@24476
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201 push cs
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pascal@24476
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202 pop ds
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pascal@24476
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203 xor bx, bx
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pascal@24476
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204
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pascal@24476
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205 and cx, 3Fh
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pascal@24476
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206 cmp [bx(bpbSectorsPerTrack)], cx
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pascal@24476
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207 jne BadParams ; verify updated and validity
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pascal@24476
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208 mov al, dh
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pascal@24476
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209 inc ax
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pascal@24476
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210 mov [bpbHeadsPerCylinder], ax
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pascal@24476
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211 BadParams:
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pascal@24476
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212
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pascal@24476
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213 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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214 ;; Load FAT (FAT12: 6KB max, FAT16: 128KB max) ;;
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pascal@24476
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215 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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216
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pascal@24476
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217 pop es ; ImageLoadSeg
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pascal@24476
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218 push es
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pascal@24476
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219
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pascal@24476
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220 mul bx ; dx:ax = 0 = LBA (LBA are relative to FAT)
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pascal@24476
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221 mov cx, word [bx(bpbSectorsPerFAT)]
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pascal@24476
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222
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pascal@24476
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223 call ReadCXSectors ; read fat and clear cx
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pascal@24476
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224
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pascal@24476
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225 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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226 ;; load the root directory in ;;
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pascal@24476
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227 ;; its entirety (16KB max) ;;
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pascal@24476
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228 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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229
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pascal@24476
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230 mov ax, 32
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pascal@24476
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231
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pascal@24476
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232 mul word [bx(bpbRootEntries)]
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pascal@24476
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233 div word [bx(bpbBytesPerSector)]
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pascal@24476
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234 xchg ax, cx ; cx = root directory size in sectors, clear ax
|
pascal@24476
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235
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pascal@24476
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236 mov al, [bpbNumberOfFATs]
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pascal@24476
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237 mul bp ; [bx(bpbSectorsPerFAT)], set by ReadCXSectors
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pascal@24476
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238
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pascal@24476
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239 push es
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pascal@24476
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240 call ReadCXSectors ; read root directory, clear cx and di
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pascal@24476
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241 pop es
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pascal@24476
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242
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pascal@24476
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243 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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244 ;; Look for the COM/EXE file to load and run ;;
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pascal@24476
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245 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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246
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pascal@24476
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247 ; es:di -> root entries array
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pascal@24476
|
248
|
pascal@24476
|
249 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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250 ;; Looks for the file/dir ProgramName ;;
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pascal@24476
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251 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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252 ;; Input: ES:DI -> root directory array ;;
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pascal@24476
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253 ;; Output: SI = cluster number ;;
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pascal@24476
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254 ;; AX = file sector count ;;
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pascal@24476
|
255 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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256
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pascal@24476
|
257 FindNameCycle:
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pascal@24476
|
258 cmp byte [es:di], ch
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pascal@24476
|
259 je FindNameFailed ; end of root directory (NULL entry found)
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pascal@24476
|
260 push di
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pascal@24476
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261 mov cl, 11
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pascal@24476
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262 mov si, ProgramName ; ds:si -> program name
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pascal@24476
|
263 repe cmpsb
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pascal@24476
|
264 pop di
|
pascal@24476
|
265 je FindNameFound
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pascal@24476
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266 add di, 32
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pascal@24476
|
267 dec word [bx(bpbRootEntries)]
|
pascal@24476
|
268 jnz FindNameCycle ; next root entry
|
pascal@24476
|
269
|
pascal@24476
|
270 FindNameFailed:
|
pascal@24476
|
271 call Error
|
pascal@24476
|
272 db "File not found."
|
pascal@24476
|
273
|
pascal@24476
|
274 FindNameFound:
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pascal@24476
|
275 push si
|
pascal@24476
|
276 mov si, [es:di+1Ah] ; si = cluster no.
|
pascal@24476
|
277 les ax, [es:di+1Ch] ; file size
|
pascal@24476
|
278 mov dx, es
|
pascal@24476
|
279 div word [bx(bpbBytesPerSector)]
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pascal@24476
|
280 cmp bx, dx ; sector aligned ?
|
pascal@24476
|
281 adc ax, bx ; file last sector
|
pascal@24476
|
282 pop di ; di = ClusterList
|
pascal@24476
|
283
|
pascal@24476
|
284 pop es ; ImageLoadSeg
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pascal@24476
|
285 push ax
|
pascal@24476
|
286
|
pascal@24476
|
287 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
288 ;; build cluster list ;;
|
pascal@24476
|
289 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
290 ;; Input: ES:0 -> FAT ;;
|
pascal@24476
|
291 ;; SI = first cluster ;;
|
pascal@24476
|
292 ;; DI = cluster list :;
|
pascal@24476
|
293 ;; CH = 0 ;;
|
pascal@24476
|
294 ;; Output: SI = cluster list ;;
|
pascal@24476
|
295 ;; CH = 0 ;;
|
pascal@24476
|
296 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
297
|
pascal@24476
|
298 push di ; up to 2 * 635K / BytesPerCluster bytes
|
pascal@24476
|
299 mov cl, 12
|
pascal@24476
|
300 ClusterLoop:
|
pascal@24476
|
301 mov [di], si
|
pascal@24476
|
302
|
pascal@24476
|
303 mov ax, es ; ax = FAT segment = ImageLoadSeg
|
pascal@24476
|
304 add si, si ; si = cluster * 2
|
pascal@24476
|
305 jnc First64
|
pascal@24476
|
306 mov ah, (1000h+ImageLoadSeg)>>8 ; adjust segment for 2nd part of FAT16
|
pascal@24476
|
307 First64:
|
pascal@24476
|
308 cmp [bx(bpbSectorsPerFAT)], cx ; 1..12 = FAT12, 16..256 = FAT16
|
pascal@24476
|
309 mov ds, ax
|
pascal@24476
|
310 jbe ReadClusterFat12
|
pascal@24476
|
311
|
pascal@24476
|
312 lodsw ; ax = next cluster
|
pascal@24476
|
313 cmp ax, 0FFF8h
|
pascal@24476
|
314 jmp ReadClusterDone
|
pascal@24476
|
315
|
pascal@24476
|
316 ReadClusterFat12:
|
pascal@24476
|
317 add si, [cs:di]
|
pascal@24476
|
318 shr si, 1 ; si = cluster * 3 / 2
|
pascal@24476
|
319
|
pascal@24476
|
320 lodsw ; ax = next cluster
|
pascal@24476
|
321 jnc ReadClusterEven
|
pascal@24476
|
322
|
pascal@24476
|
323 rol ax, cl
|
pascal@24476
|
324
|
pascal@24476
|
325 ReadClusterEven:
|
pascal@24476
|
326 and ax, 0FFFh ; mask cluster value
|
pascal@24476
|
327 cmp ax, 0FF8h
|
pascal@24476
|
328
|
pascal@24476
|
329 ReadClusterDone:
|
pascal@24476
|
330 push cs
|
pascal@24476
|
331 pop ds
|
pascal@24476
|
332 inc di
|
pascal@24476
|
333 inc di
|
pascal@24476
|
334 xchg ax, si
|
pascal@24476
|
335 jc ClusterLoop
|
pascal@24476
|
336 pop si
|
pascal@24476
|
337 pop di ; file size in sectors
|
pascal@24476
|
338
|
pascal@24476
|
339 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
340 ;; Load the entire file ;;
|
pascal@24476
|
341 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
342 ;; Input: ES:0 -> buffer ;;
|
pascal@24476
|
343 ;; SI = cluster list ;;
|
pascal@24476
|
344 ;; DI = file sectors ;;
|
pascal@24476
|
345 ;; CH = 0 ;;
|
pascal@24476
|
346 ;; Output: BP:0 -> buffer ;;
|
pascal@24476
|
347 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
348
|
pascal@24476
|
349 push es
|
pascal@24476
|
350
|
pascal@24476
|
351 ReadClusters:
|
pascal@24476
|
352 lodsw
|
pascal@24476
|
353 dec ax
|
pascal@24476
|
354 dec ax
|
pascal@24476
|
355
|
pascal@24476
|
356 mov cl, [bx(bpbSectorsPerCluster)]
|
pascal@24476
|
357 mul cx ; cx = sector count (ch = 0)
|
pascal@24476
|
358
|
pascal@24476
|
359 add ax, bp ; LBA for cluster data
|
pascal@24476
|
360 adc dx, bx ; dx:ax = LBA
|
pascal@24476
|
361
|
pascal@24476
|
362 call ReadSector ; clear cx
|
pascal@24476
|
363
|
pascal@24476
|
364 jne ReadClusters
|
pascal@24476
|
365
|
pascal@24476
|
366 pop bp ; ImageLoadSeg
|
pascal@24476
|
367
|
pascal@24476
|
368 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
369 ;; Type detection, .COM or .EXE? ;;
|
pascal@24476
|
370 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
371
|
pascal@24476
|
372 mov ds, bp ; bp=ds=seg the file is loaded to
|
pascal@24476
|
373
|
pascal@24476
|
374 add bp, [bx+08h] ; bp = image base
|
pascal@24476
|
375 mov ax, [bx+06h] ; ax = reloc items
|
pascal@24476
|
376 mov di, [bx+18h] ; di = reloc table pointer
|
pascal@24476
|
377
|
pascal@24476
|
378 cmp word [bx], 5A4Dh ; "MZ" signature?
|
pascal@24476
|
379 je RelocateEXE ; yes, it's an EXE program
|
pascal@24476
|
380
|
pascal@24476
|
381 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
382 ;; Setup and run a .COM program ;;
|
pascal@24476
|
383 ;; Set CS=DS=ES=SS SP=0 IP=100h ;;
|
pascal@24476
|
384 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
385
|
pascal@24476
|
386 mov bp, ImageLoadSeg-10h ; "org 100h" stuff :)
|
pascal@24476
|
387 mov ss, bp
|
pascal@24476
|
388 xor sp, sp
|
pascal@24476
|
389 push bp ; cs, ds and es
|
pascal@24476
|
390 mov bh, 1 ; ip
|
pascal@24476
|
391 jmp short Run
|
pascal@24476
|
392
|
pascal@24476
|
393 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
394 ;; Relocate, setup and run a .EXE program ;;
|
pascal@24476
|
395 ;; Set CS:IP, SS:SP, DS, ES and AX according ;;
|
pascal@24476
|
396 ;; to wiki.osdev.org/MZ#Initial_Program_State ;;
|
pascal@24476
|
397 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
398
|
pascal@24476
|
399 ReloCycle:
|
pascal@24476
|
400 add [di+2], bp ; item seg (abs)
|
pascal@24476
|
401 les si, [di] ; si = item ofs, es = item seg
|
pascal@24476
|
402 add [es:si], bp ; fixup
|
pascal@24476
|
403 scasw ; di += 2
|
pascal@24476
|
404 scasw ; point to next entry
|
pascal@24476
|
405
|
pascal@24476
|
406 RelocateEXE:
|
pascal@24476
|
407 dec ax ; 32768 max (128KB table)
|
pascal@24476
|
408 jns ReloCycle ; leave with ax=0ffffh: both FCB in the
|
pascal@24476
|
409 ; PSP don't have a valid drive identifier
|
pascal@24476
|
410 les si, [bx+0Eh]
|
pascal@24476
|
411 add si, bp
|
pascal@24476
|
412 mov ss, si ; ss for EXE
|
pascal@24476
|
413 mov sp, es ; sp for EXE
|
pascal@24476
|
414
|
pascal@24476
|
415 lea si, [bp-10h] ; ds and es both point to the segment
|
pascal@24476
|
416 push si ; containing the PSP structure
|
pascal@24476
|
417
|
pascal@24476
|
418 add bp, [bx+16h] ; cs for EXE
|
pascal@24476
|
419 mov bx, [bx+14h] ; ip for EXE
|
pascal@24476
|
420 Run:
|
pascal@24476
|
421 pop ds
|
pascal@24476
|
422 push bp
|
pascal@24476
|
423 push bx
|
pascal@24476
|
424 push ds
|
pascal@24476
|
425 pop es
|
pascal@24476
|
426
|
pascal@24476
|
427 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
428 ;; Set the magic numbers so the program knows that it ;;
|
pascal@24476
|
429 ;; has been loaded by this bootsector and not by MS-DOS ;;
|
pascal@24476
|
430 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
431 mov si, 16381 ; prime number 2**14-3
|
pascal@24476
|
432 mov di, 32749 ; prime number 2**15-19
|
pascal@24476
|
433 mov bp, 65521 ; prime number 2**16-15
|
pascal@24476
|
434
|
pascal@24476
|
435 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
436 ;; All done, transfer control to the program now ;;
|
pascal@24476
|
437 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
438 retf
|
pascal@24476
|
439
|
pascal@24476
|
440 ReadCXSectors:
|
pascal@24476
|
441 mov bp, cx
|
pascal@24476
|
442 add bp, ax ; adjust LBA for cluster data
|
pascal@24476
|
443
|
pascal@24476
|
444 mov di, cx ; no file size limit
|
pascal@24476
|
445
|
pascal@24476
|
446 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
447 ;; Reads sectors using BIOS Int 13h ;;
|
pascal@24476
|
448 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
449 ;; Input: DX:AX = LBA relative to FAT ;;
|
pascal@24476
|
450 ;; BX = 0 ;;
|
pascal@24476
|
451 ;; CX = sector count ;;
|
pascal@24476
|
452 ;; DI = file sectors ;;
|
pascal@24476
|
453 ;; ES:BX -> buffer address ;;
|
pascal@24476
|
454 ;; Output: ES:BX -> next address ;;
|
pascal@24476
|
455 ;; BX = 0 ;;
|
pascal@24476
|
456 ;; CX or DI = 0 ;;
|
pascal@24476
|
457 ;; DL = drive number ;;
|
pascal@24476
|
458 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
459
|
pascal@24476
|
460 ReadSector:
|
pascal@24476
|
461 add ax, [bx(bpbHiddenSectors)]
|
pascal@24476
|
462 adc dx, [bx(bpbHiddenSectors)+2]
|
pascal@24476
|
463 add ax, [bx(bpbReservedSectors)]
|
pascal@24476
|
464
|
pascal@24476
|
465 push si
|
pascal@24476
|
466 ReadSectorNext:
|
pascal@24476
|
467 adc dx, bx
|
pascal@24476
|
468 push di
|
pascal@24476
|
469 push cx
|
pascal@24476
|
470
|
pascal@24476
|
471 push bx
|
pascal@24476
|
472 push bx
|
pascal@24476
|
473 push dx ; 32-bit LBA: up to 2TB
|
pascal@24476
|
474 push ax
|
pascal@24476
|
475 push es
|
pascal@24476
|
476 push bx
|
pascal@24476
|
477 inc bx ; sector count word = 1
|
pascal@24476
|
478 push bx
|
pascal@24476
|
479 dec bx
|
pascal@24476
|
480 mov di, 16 ; packet size byte = 16, reserved byte = 0
|
pascal@24476
|
481 push di
|
pascal@24476
|
482
|
pascal@24476
|
483 xchg ax, cx ; save low LBA
|
pascal@24476
|
484 xchg ax, dx ; get high LBA
|
pascal@24476
|
485 cwd ; clear dx (LBA offset <2TB)
|
pascal@24476
|
486 div word [bx(bpbSectorsPerTrack)] ; up to 8GB disks
|
pascal@24476
|
487
|
pascal@24476
|
488 xchg ax, cx ; restore low LBA, save high LBA / SPT
|
pascal@24476
|
489 div word [bx(bpbSectorsPerTrack)]
|
pascal@24476
|
490 ; ax = LBA / SPT
|
pascal@24476
|
491 ; dx = LBA % SPT = sector - 1
|
pascal@24476
|
492 inc dx
|
pascal@24476
|
493
|
pascal@24476
|
494 xchg cx, dx ; restore high LBA / SPT, save sector no.
|
pascal@24476
|
495 div word [bx(bpbHeadsPerCylinder)]
|
pascal@24476
|
496 ; ax = (LBA / SPT) / HPC = cylinder
|
pascal@24476
|
497 ; dx = (LBA / SPT) % HPC = head
|
pascal@24476
|
498 mov ch, al
|
pascal@24476
|
499 ; ch = LSB 0...7 of cylinder no.
|
pascal@24476
|
500 mov al, 64
|
pascal@24476
|
501 mul ah
|
pascal@24476
|
502 or cl, al
|
pascal@24476
|
503 ; cl = MSB 8...9 of cylinder no. + sector no.
|
pascal@24476
|
504 mov dh, dl
|
pascal@24476
|
505 ; dh = head no.
|
pascal@24476
|
506
|
pascal@24476
|
507 ReadSectorRetry:
|
pascal@24476
|
508 mov dl, [bx]
|
pascal@24476
|
509 ; dl = drive no.
|
pascal@24476
|
510 mov ah, 42h ; ah = 42h = extended read function no.
|
pascal@24476
|
511 mov si, sp
|
pascal@24476
|
512 int 13h ; extended read sectors (DL, DS:SI)
|
pascal@24476
|
513 jnc ReadSectorNextSegment
|
pascal@24476
|
514
|
pascal@24476
|
515 mov ax, 201h ; al = sector count = 1
|
pascal@24476
|
516 ; ah = 2 = read function no.
|
pascal@24476
|
517 int 13h ; read sectors (AL, CX, DX, ES:BX)
|
pascal@24476
|
518
|
pascal@24476
|
519 jnc ReadSectorNextSegment
|
pascal@24476
|
520 cbw ; ah = 0 = reset function
|
pascal@24476
|
521 int 13h ; reset drive (DL)
|
pascal@24476
|
522
|
pascal@24476
|
523 dec di
|
pascal@24476
|
524 jnz ReadSectorRetry ; extra attempt
|
pascal@24476
|
525
|
pascal@24476
|
526 call Error
|
pascal@24476
|
527 db "Read error."
|
pascal@24476
|
528
|
pascal@24476
|
529 ReadSectorNextSegment:
|
pascal@24476
|
530
|
pascal@24476
|
531 pop ax ; al = 16
|
pascal@24476
|
532 mul byte [bx(bpbBytesPerSector)+1] ; = (bpbBytesPerSector/256)*16
|
pascal@24476
|
533 pop cx ; sector count = 1
|
pascal@24476
|
534 pop bx
|
pascal@24476
|
535 add [si+6], ax ; adjust segment for next sector
|
pascal@24476
|
536 pop es ; es:0 updated
|
pascal@24476
|
537 pop ax
|
pascal@24476
|
538 pop dx
|
pascal@24476
|
539 pop di
|
pascal@24476
|
540 pop di
|
pascal@24476
|
541
|
pascal@24476
|
542 add ax, cx ; adjust LBA for next sector
|
pascal@24476
|
543
|
pascal@24476
|
544 pop cx ; cluster sectors to read
|
pascal@24476
|
545 pop di ; file sectors to read
|
pascal@24476
|
546 dec di ; keep C
|
pascal@24476
|
547 loopne ReadSectorNext ; until cluster sector count or file sector count is reached
|
pascal@24476
|
548 pop si
|
pascal@24476
|
549 mov dx, [bx] ; pass the BIOS boot drive to Run or Error
|
pascal@24476
|
550
|
pascal@24476
|
551 ret
|
pascal@24476
|
552
|
pascal@24476
|
553 ;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
554 ;; Error Messaging Code ;;
|
pascal@24476
|
555 ;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
556
|
pascal@24476
|
557 Error:
|
pascal@24476
|
558 pop si
|
pascal@24476
|
559 mov ah, 0Eh
|
pascal@24476
|
560 mov bl, 7
|
pascal@24476
|
561
|
pascal@24476
|
562 PutStr:
|
pascal@24476
|
563 lodsb
|
pascal@24476
|
564 int 10h
|
pascal@24476
|
565 cmp al, "."
|
pascal@24476
|
566 jne PutStr
|
pascal@24476
|
567
|
pascal@24476
|
568 cbw
|
pascal@24476
|
569 int 16h ; wait for a key...
|
pascal@24476
|
570 int 19h ; bootstrap
|
pascal@24476
|
571
|
pascal@24476
|
572 Stop:
|
pascal@24476
|
573 hlt
|
pascal@24476
|
574 jmp short Stop
|
pascal@24476
|
575
|
pascal@24476
|
576 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
577 ;; Fill free space with zeroes ;;
|
pascal@24476
|
578 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
579
|
pascal@24476
|
580 times (512-13-($-$$)) db 0
|
pascal@24476
|
581
|
pascal@24476
|
582 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
583 ;; Name of the file to load and run ;;
|
pascal@24476
|
584 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
585
|
pascal@24476
|
586 ProgramName db "STARTUP BIN" ; name and extension each must be
|
pascal@24476
|
587 ; padded with spaces (11 bytes total)
|
pascal@24476
|
588
|
pascal@24476
|
589 ;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
590 ;; End of the sector ID ;;
|
pascal@24476
|
591 ;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
592
|
pascal@24476
|
593 ClusterList dw 0AA55h ; BIOS checks for this ID
|