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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 boot32.asm -f bin -o boot32.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@24535
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14 ;; - FAT32 supported using BIOS int 13h function 42h (IOW, it will only ;;
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pascal@24535
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15 ;; work with modern BIOSes supporting HDDs bigger than 8 GB) ;;
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pascal@24476
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16 ;; ;;
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pascal@24476
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17 ;; - Loads a 16-bit executable file in the MS-DOS .COM or .EXE format ;;
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pascal@24476
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18 ;; from the root directory of a disk and transfers control to it ;;
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pascal@24476
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19 ;; (the "ProgramName" variable holds the name of the file to be loaded) ;;
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pascal@24525
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20 ;; Its maximum size can be up to 636KB without Extended BIOS Data area. ;;
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pascal@24476
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21 ;; ;;
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pascal@24476
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22 ;; - Prints an error if the file isn't found or couldn't be read ;;
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pascal@24476
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23 ;; ("File not found" or "Read error") ;;
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pascal@24476
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24 ;; and waits for a key to be pressed, then executes the Int 19h ;;
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pascal@24476
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25 ;; instruction and lets the BIOS continue bootstrap. ;;
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pascal@24476
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26 ;; ;;
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pascal@24476
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27 ;; ;;
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pascal@24476
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28 ;; Known Bugs: ;;
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pascal@24476
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29 ;; ~~~~~~~~~~~ ;;
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pascal@24476
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30 ;; - 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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31 ;; on my HDD and an 8GB USB stick. ;;
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pascal@24476
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32 ;; ;;
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pascal@24476
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33 ;; ;;
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pascal@24476
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34 ;; Memory Layout: ;;
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pascal@24476
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35 ;; ~~~~~~~~~~~~~~ ;;
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pascal@24476
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36 ;; The diagram below shows the typical memory layout. The actual location ;;
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pascal@24476
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37 ;; 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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38 ;; reserves memory for its Extended BIOS Data Area just below A0000H and ;;
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pascal@24476
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39 ;; reports less than 640 KB of RAM via its Int 12H function. ;;
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pascal@24476
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40 ;; ;;
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pascal@24476
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41 ;; physical address ;;
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pascal@24476
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42 ;; +------------------------+ 00000H ;;
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pascal@24476
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43 ;; | Interrupt Vector Table | ;;
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pascal@24476
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44 ;; +------------------------+ 00400H ;;
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pascal@24476
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45 ;; | BIOS Data Area | ;;
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pascal@24476
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46 ;; +------------------------+ 00500H ;;
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pascal@24476
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47 ;; | PrtScr Status / Unused | ;;
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pascal@24476
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48 ;; +------------------------+ 00600H ;;
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pascal@24476
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49 ;; | Loaded Image | ;;
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pascal@24476
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50 ;; +------------------------+ nnnnnH ;;
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pascal@24476
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51 ;; | Available Memory | ;;
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pascal@24525
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52 ;; +------------------------+ A0000H - 2KB ;;
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pascal@24476
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53 ;; | Boot Sector | ;;
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pascal@24525
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54 ;; +------------------------+ A0000H - 1.5KB ;;
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pascal@24525
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55 ;; | 1.5KB Boot Stack | ;;
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pascal@24476
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56 ;; +------------------------+ A0000H ;;
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pascal@24476
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57 ;; | Video RAM | ;;
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pascal@24476
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58 ;; ;;
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pascal@24476
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59 ;; ;;
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pascal@24476
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60 ;; Boot Image Startup (register values): ;;
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pascal@24476
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61 ;; ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ;;
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pascal@24945
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62 ;; ax = 0ffffh (both FCB in the PSP don't have a valid drive identifier), ;;
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pascal@24945
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63 ;; bx = cx = 0, dl = BIOS boot drive number (e.g. 0, 80H) ;;
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pascal@24476
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64 ;; cs:ip = program entry point ;;
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pascal@24476
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65 ;; ss:sp = program stack (don't confuse with boot sector's stack) ;;
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pascal@24476
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66 ;; COM program defaults: cs = ds = es = ss = 50h, sp = 0, ip = 100h ;;
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pascal@24476
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67 ;; EXE program defaults: ds = es = EXE data - 10h (fake MS-DOS psp), ;;
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pascal@24476
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68 ;; cs:ip and ss:sp depends on EXE header ;;
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pascal@24476
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69 ;; Magic numbers: ;;
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pascal@24476
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70 ;; si = 16381 (prime number 2**14-3) ;;
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pascal@24476
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71 ;; di = 32749 (prime number 2**15-19) ;;
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pascal@24476
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72 ;; bp = 65521 (prime number 2**16-15) ;;
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pascal@24476
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73 ;; The magic numbers let the program know whether it has been loaded by ;;
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pascal@24476
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74 ;; this boot sector or by MS-DOS, which may be handy for universal, bare- ;;
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pascal@24476
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75 ;; metal and MS-DOS programs. ;;
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pascal@24945
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76 ;; The command line contains no arguments. ;;
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pascal@24476
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77 ;; ;;
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pascal@24476
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78 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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79
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pascal@24491
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80 %define bx(label) bx+label-boot
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pascal@24491
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81
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pascal@24476
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82 [BITS 16]
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pascal@24476
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83
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pascal@24478
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84 ImageLoadSeg equ 60h ; <=07Fh because of "push byte ImageLoadSeg" instructions
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pascal@24525
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85 StackSize equ 1536
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pascal@24476
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86
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pascal@24476
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87 [SECTION .text]
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pascal@24476
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88 [ORG 0]
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pascal@24476
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89
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pascal@24476
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90 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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91 ;; Boot sector starts here ;;
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pascal@24476
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92 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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93
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pascal@24491
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94 boot:
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pascal@24491
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95 HiLBA equ boot+0
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pascal@24476
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96 jmp short start ; MS-DOS/Windows checks for this jump
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pascal@24476
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97 nop
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pascal@24476
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98 bsOemName DB "BootProg" ; 0x03
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pascal@24476
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99
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pascal@24476
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100 ;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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101 ;; BPB1 starts here ;;
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pascal@24476
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102 ;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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103
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pascal@24479
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104 bpbBytesPerSector DW 0 ; 0x0B
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pascal@24479
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105 bpbSectorsPerCluster DB 0 ; 0x0D
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pascal@24479
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106 bpbReservedSectors DW 0 ; 0x0E
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pascal@24479
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107 bpbNumberOfFATs DB 0 ; 0x10
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pascal@24479
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108 bpbRootEntries DW 0 ; 0x11
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pascal@24479
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109 bpbTotalSectors DW 0 ; 0x13
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pascal@24479
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110 bpbMedia DB 0 ; 0x15
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pascal@24479
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111 bpbSectorsPerFAT DW 0 ; 0x16
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pascal@24479
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112 bpbSectorsPerTrack DW 0 ; 0x18
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pascal@24479
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113 bpbHeadsPerCylinder DW 0 ; 0x1A
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pascal@24479
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114 bpbHiddenSectors DD 0 ; 0x1C
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pascal@24479
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115 bpbTotalSectorsBig DD 0 ; 0x20
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pascal@24476
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116
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pascal@24476
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117 ;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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118 ;; BPB1 ends here ;;
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pascal@24476
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119 ;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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120
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pascal@24476
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121 ;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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122 ;; BPB2 starts here ;;
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pascal@24476
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123 ;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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124
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pascal@24479
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125 bsSectorsPerFAT32 DD 0 ; 0x24
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pascal@24479
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126 bsExtendedFlags DW 0 ; 0x28
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pascal@24479
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127 bsFSVersion DW 0 ; 0x2A
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pascal@24479
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128 bsRootDirectoryClusterNo DD 0 ; 0x2C
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pascal@24479
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129 bsFSInfoSectorNo DW 0 ; 0x30
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pascal@24479
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130 bsBackupBootSectorNo DW 0 ; 0x32
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pascal@24479
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131 bsreserved times 12 DB 0 ; 0x34
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pascal@24479
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132 bsDriveNumber DB 0 ; 0x40
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pascal@24479
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133 bsreserved1 DB 0 ; 0x41
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pascal@24479
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134 bsExtendedBootSignature DB 0 ; 0x42
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pascal@24479
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135 bsVolumeSerialNumber DD 0 ; 0x43
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pascal@24476
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136 bsVolumeLabel DB "NO NAME " ; 0x47
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pascal@24476
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137 bsFileSystemName DB "FAT32 " ; 0x52
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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 ;; BPB2 ends 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 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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144 ;; Boot sector code starts here ;;
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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 start:
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pascal@24476
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148 cld
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pascal@24476
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149
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pascal@24476
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150 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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151 ;; How much RAM is there? ;;
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pascal@24476
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152 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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153
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pascal@24476
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154 int 12h ; get conventional memory size (in KBs)
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pascal@24525
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155 dec ax
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pascal@24525
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156 dec ax ; reserve 2K bytes for the code and the stack
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pascal@24525
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157 mov cx, 106h
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pascal@24525
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158 shl ax, cl ; and convert it to 16-byte paragraphs
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pascal@24476
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159
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pascal@24476
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160 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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161 ;; Reserve memory for the boot sector and its stack ;;
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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@24525
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164 mov es, ax ; cs:0 = ds:0 = ss:0 -> top - 512 - StackSize
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pascal@24525
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165 mov ss, ax
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pascal@24525
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166 mov sp, 512+StackSize ; bytes 0-511 are reserved for the boot code
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pascal@24476
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167
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pascal@24476
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168 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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169 ;; Copy ourselves to top of memory ;;
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pascal@24476
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170 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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171
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pascal@24476
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172 mov si, 7C00h
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pascal@24476
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173 xor di, di
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pascal@24476
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174 mov ds, di
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pascal@24478
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175 rep movsw
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pascal@24476
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176
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pascal@24476
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177 ;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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178 ;; Jump to the copy ;;
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pascal@24476
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179 ;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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180
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pascal@24476
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181 push es
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pascal@24478
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182 push byte main
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pascal@24476
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183 retf
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pascal@24476
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184
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pascal@24476
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185 main:
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pascal@24476
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186 push cs
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pascal@24476
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187 pop ds
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pascal@24476
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188
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pascal@24491
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189 xor bx, bx
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pascal@24491
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190 mov [bx(bsDriveNumber)], dx ; store BIOS boot drive number
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pascal@24476
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191
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pascal@24491
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192 and byte [bx(bsRootDirectoryClusterNo+3)], 0Fh ; mask cluster value
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pascal@24491
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193 mov esi, [bx(bsRootDirectoryClusterNo)] ; esi=cluster # of root dir
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pascal@24476
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194
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pascal@24476
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195 RootDirReadContinue:
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pascal@24478
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196 push byte ImageLoadSeg
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pascal@24478
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197 pop es
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pascal@24478
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198 call ReadCluster ; read one cluster of root dir
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pascal@24478
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199 pushf ; save carry="not last cluster" flag
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pascal@24476
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200
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pascal@24476
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201 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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202 ;; Look for the COM/EXE file to load and run ;;
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pascal@24476
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203 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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204
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pascal@24476
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205 xor di, di ; es:di -> root entries array
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pascal@24476
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206
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pascal@24476
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207 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24478
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208 ;; Looks for a file/dir by its name ;;
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pascal@24476
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209 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24478
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210 ;; Input: DS:SI -> file name (11 chars) ;;
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pascal@24478
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211 ;; ES:DI -> root directory array ;;
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pascal@24478
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212 ;; DX = number of root entries ;;
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pascal@24525
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213 ;; BP = paragraphs in sector ;;
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pascal@24476
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214 ;; Output: ESI = cluster number ;;
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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@24478
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217 FindName:
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pascal@24476
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218 FindNameCycle:
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pascal@24525
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219 cmp byte [es:di], bh
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pascal@24478
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220 je ErrFind ; end of root directory (NULL entry found)
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pascal@24478
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221 FindNameNotEnd:
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pascal@24478
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222 pusha
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pascal@24525
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223 mov cl, 11
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pascal@24525
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224 mov si, ProgramName ; ds:si -> program name
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pascal@24476
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225 repe cmpsb
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pascal@24525
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226 je FindNameFound
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pascal@24478
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227 popa
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pascal@24525
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228 add di, byte 32
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pascal@24476
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229 dec bp
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pascal@24476
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230 dec bp
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pascal@24476
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231 jnz FindNameCycle ; next root entry
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pascal@24478
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232 popf ; restore carry="not last cluster" flag
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pascal@24476
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233 jc RootDirReadContinue ; continue to the next root dir cluster
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pascal@24478
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234 ErrFind:
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pascal@24478
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235 call Error ; end of root directory (dir end reached)
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pascal@24476
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236 db "File not found."
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pascal@24476
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237 FindNameFound:
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pascal@24525
|
238 push word [es:di+14h-11]
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pascal@24525
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239 push word [es:di+1Ah-11]
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pascal@24478
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240 pop esi ; esi = cluster no. cx = 0
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pascal@24476
|
241
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pascal@24525
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242 dec dword [es:di+1Ch-11] ; load ((n - 1)/256)*16 +1 paragraphs
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pascal@24525
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243 imul di, [es:di+1Ch+1-11], byte 16 ; file size in paragraphs (full pages)
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pascal@24476
|
244
|
pascal@24476
|
245 ;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
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246 ;; Load the entire file ;;
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pascal@24476
|
247 ;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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248
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pascal@24476
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249 push es
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pascal@24476
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250 FileReadContinue:
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pascal@24476
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251 push di
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pascal@24478
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252 call ReadCluster ; read one cluster of root dir
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pascal@24476
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253 mov di, es
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pascal@24478
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254 add di, bp
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pascal@24478
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255 mov es, di ; es:bx updated
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pascal@24476
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256 pop di
|
pascal@24478
|
257
|
pascal@24476
|
258 sub di, bp
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pascal@24476
|
259 jae FileReadContinue
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pascal@24943
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260 xor ax, ax
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pascal@24476
|
261 pop bp
|
pascal@24476
|
262
|
pascal@24476
|
263 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
|
264 ;; Type detection, .COM or .EXE? ;;
|
pascal@24476
|
265 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
266
|
pascal@24476
|
267 mov ds, bp ; bp=ds=seg the file is loaded to
|
pascal@24535
|
268
|
pascal@24476
|
269 add bp, [bx+08h] ; bp = image base
|
pascal@24476
|
270 mov di, [bx+18h] ; di = reloc table pointer
|
pascal@24476
|
271
|
pascal@24476
|
272 cmp word [bx], 5A4Dh ; "MZ" signature?
|
pascal@24476
|
273 je RelocateEXE ; yes, it's an EXE program
|
pascal@24476
|
274
|
pascal@24476
|
275 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
276 ;; Setup and run a .COM program ;;
|
pascal@24535
|
277 ;; Set CS=DS=ES=SS SP=0 IP=100h ;;
|
pascal@24535
|
278 ;; AX=0ffffh BX=0 CX=0 DX=drive ;;
|
pascal@24942
|
279 ;; and cmdline=void ;;
|
pascal@24476
|
280 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
281
|
pascal@24535
|
282 mov di, 100h ; ip
|
pascal@24476
|
283 mov bp, ImageLoadSeg-10h ; "org 100h" stuff :)
|
pascal@24476
|
284 mov ss, bp
|
pascal@24476
|
285 xor sp, sp
|
pascal@24476
|
286 push bp ; cs, ds and es
|
pascal@24476
|
287 jmp short Run
|
pascal@24476
|
288
|
pascal@24476
|
289 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
290 ;; Relocate, setup and run a .EXE program ;;
|
pascal@24476
|
291 ;; Set CS:IP, SS:SP, DS, ES and AX according ;;
|
pascal@24476
|
292 ;; to wiki.osdev.org/MZ#Initial_Program_State ;;
|
pascal@24942
|
293 ;; AX=0ffffh BX=0 CX=0 DX=drive cmdline=void ;;
|
pascal@24476
|
294 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
295
|
pascal@24476
|
296 ReloCycle:
|
pascal@24476
|
297 add [di+2], bp ; item seg (abs)
|
pascal@24476
|
298 les si, [di] ; si = item ofs, es = item seg
|
pascal@24476
|
299 add [es:si], bp ; fixup
|
pascal@24525
|
300 scasw ; di += 2
|
pascal@24525
|
301 scasw ; point to next entry
|
pascal@24476
|
302
|
pascal@24476
|
303 RelocateEXE:
|
pascal@24942
|
304 dec word [bx+06h] ; reloc items, 32768 max (128KB table)
|
pascal@24942
|
305 jns ReloCycle
|
pascal@24942
|
306
|
pascal@24945
|
307 les si, [bx+0Eh]
|
pascal@24945
|
308 add si, bp
|
pascal@24945
|
309 mov ss, si ; ss for EXE
|
pascal@24945
|
310 mov sp, es ; sp for EXE
|
pascal@24476
|
311
|
pascal@24476
|
312 lea si, [bp-10h] ; ds and es both point to the segment
|
pascal@24476
|
313 push si ; containing the PSP structure
|
pascal@24476
|
314
|
pascal@24476
|
315 add bp, [bx+16h] ; cs for EXE
|
pascal@24535
|
316 mov di, [bx+14h] ; ip for EXE
|
pascal@24476
|
317 Run:
|
pascal@24476
|
318 pop ds
|
pascal@24476
|
319 push bp
|
pascal@24535
|
320 push di
|
pascal@24476
|
321 push ds
|
pascal@24476
|
322 pop es
|
pascal@24942
|
323 mov [80h], ax ; clear cmdline
|
pascal@24942
|
324 dec ax ; both FCB in the PSP don't have a valid drive identifier
|
pascal@24476
|
325
|
pascal@24476
|
326 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
327 ;; Set the magic numbers so the program knows that it ;;
|
pascal@24476
|
328 ;; has been loaded by this bootsector and not by MS-DOS ;;
|
pascal@24476
|
329 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
330 mov si, 16381 ; prime number 2**14-3
|
pascal@24476
|
331 mov di, 32749 ; prime number 2**15-19
|
pascal@24476
|
332 mov bp, 65521 ; prime number 2**16-15
|
pascal@24476
|
333
|
pascal@24476
|
334 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
335 ;; All done, transfer control to the program now ;;
|
pascal@24476
|
336 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
337 retf
|
pascal@24476
|
338
|
pascal@24525
|
339 ReadCluster:
|
pascal@24525
|
340 mov bp, [bx(bpbBytesPerSector)]
|
pascal@24525
|
341 shr bp, 4 ; bp = paragraphs per sector
|
pascal@24945
|
342 add eax, byte 1 ; adjust LBA for next sector
|
pascal@24525
|
343 inc cx
|
pascal@24525
|
344 loop ReadSectorLBA
|
pascal@24525
|
345
|
pascal@24478
|
346 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24478
|
347 ;; Reads a FAT32 cluster ;;
|
pascal@24478
|
348 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24478
|
349 ;; Inout: ES:BX -> buffer ;;
|
pascal@24478
|
350 ;; ESI = cluster no ;;
|
pascal@24478
|
351 ;; Output: ESI = next cluster ;;
|
pascal@24525
|
352 ;; BP -> para / sector ;;
|
pascal@24478
|
353 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
354
|
pascal@24945
|
355 imul ax, bp, byte 4 ; ax=# of FAT32 entries per sector
|
pascal@24478
|
356 cwde
|
pascal@24525
|
357 lea edi, [esi-2] ; esi=cluster #
|
pascal@24476
|
358 xchg eax, esi
|
pascal@24476
|
359 cdq
|
pascal@24478
|
360 div esi ; eax=FAT sector #, edx=entry # in sector
|
pascal@24476
|
361
|
pascal@24525
|
362 imul si, dx, byte 4 ; si=entry # in sector, clear C
|
pascal@24491
|
363 mov word [bx(HiLBA)], bx
|
pascal@24478
|
364 call ReadSectorLBAabsolute ; read 1 FAT32 sector
|
pascal@24476
|
365
|
pascal@24478
|
366 and byte [es:si+3], 0Fh ; mask cluster value
|
pascal@24478
|
367 mov esi, [es:si] ; esi=next cluster #
|
pascal@24476
|
368
|
pascal@24525
|
369 movzx eax, byte [bx(bpbNumberOfFATs)]
|
pascal@24525
|
370 mul dword [bx(bsSectorsPerFAT32)]
|
pascal@24525
|
371 mov word [bx(HiLBA)], dx
|
pascal@24525
|
372
|
pascal@24525
|
373 xchg eax, edi
|
pascal@24491
|
374 movzx ecx, byte [bx(bpbSectorsPerCluster)]
|
pascal@24945
|
375 mul ecx ; edx:eax=sector number in data area
|
pascal@24476
|
376
|
pascal@24525
|
377 add eax, edi
|
pascal@24491
|
378 adc word [bx(HiLBA)], dx
|
pascal@24476
|
379
|
pascal@24478
|
380 ReadSectorLBAabsolute:
|
pascal@24525
|
381 mov dx, word [bx(bpbReservedSectors)]
|
pascal@24478
|
382 add eax, edx
|
pascal@24491
|
383 adc word [bx(HiLBA)], bx
|
pascal@24491
|
384 add eax, [bx(bpbHiddenSectors)]
|
pascal@24476
|
385
|
pascal@24478
|
386 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24478
|
387 ;; Reads a sector using BIOS Int 13h fn 42h ;;
|
pascal@24478
|
388 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24478
|
389 ;; Input: EAX = LBA ;;
|
pascal@24478
|
390 ;; CX = sector count ;;
|
pascal@24478
|
391 ;; ES:BX -> buffer address ;;
|
pascal@24478
|
392 ;; Output: CF = 0 if no more sectors ;;
|
pascal@24478
|
393 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
394
|
pascal@24476
|
395 ReadSectorLBA:
|
pascal@24535
|
396 adc word [bx(HiLBA)], bx
|
pascal@24535
|
397 mov dx, [bx(bsDriveNumber)] ; restore BIOS boot drive number
|
pascal@24476
|
398 pusha
|
pascal@24476
|
399
|
pascal@24478
|
400 push bx
|
pascal@24491
|
401 push word [bx(HiLBA)] ; 48-bit LBA
|
pascal@24478
|
402 push eax
|
pascal@24476
|
403 push es
|
pascal@24476
|
404 push bx
|
pascal@24478
|
405 push byte 1 ; sector count word = 1
|
pascal@24525
|
406 push byte 16 ; packet size byte = 16, reserved byte = 0
|
pascal@24525
|
407
|
pascal@24525
|
408 ReadSectorLBARetry:
|
pascal@24525
|
409 mov si, sp
|
pascal@24478
|
410 mov ah, 42h ; ah = 42h = extended read function no.
|
pascal@24478
|
411 int 13h ; extended read sectors (DL, DS:SI)
|
pascal@24478
|
412 jnc ReadSuccess ; CF = 0 if no error
|
pascal@24476
|
413
|
pascal@24945
|
414 xor ax, ax ; ah = 0 = reset function
|
pascal@24476
|
415 int 13h ; reset drive (DL)
|
pascal@24476
|
416
|
pascal@24525
|
417 dec bp
|
pascal@24525
|
418 jnz ReadSectorLBARetry
|
pascal@24525
|
419
|
pascal@24476
|
420 call Error
|
pascal@24476
|
421 db "Read error."
|
pascal@24476
|
422
|
pascal@24478
|
423 ReadSuccess:
|
pascal@24476
|
424
|
pascal@24476
|
425 popa ; sp += 16
|
pascal@24478
|
426
|
pascal@24478
|
427 popa
|
pascal@24478
|
428
|
pascal@24476
|
429 stc
|
pascal@24478
|
430 loop ReadSectorNext
|
pascal@24476
|
431
|
pascal@24478
|
432 cmp esi, 0FFFFFF8h ; carry=0 if last cluster, and carry=1 otherwise
|
pascal@24476
|
433
|
pascal@24478
|
434 ReadSectorNext:
|
pascal@24476
|
435 ret
|
pascal@24476
|
436
|
pascal@24942
|
437 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24942
|
438 ;; Fill free space with zeroes ;;
|
pascal@24942
|
439 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24942
|
440
|
pascal@24942
|
441 times (512-13-20-($-$$)) db 0
|
pascal@24942
|
442
|
pascal@24476
|
443 ;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
444 ;; Error Messaging Code ;;
|
pascal@24476
|
445 ;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
446
|
pascal@24476
|
447 Error:
|
pascal@24476
|
448 pop si
|
pascal@24478
|
449 puts:
|
pascal@24476
|
450 mov ah, 0Eh
|
pascal@24476
|
451 mov bl, 7
|
pascal@24476
|
452 lodsb
|
pascal@24476
|
453 int 10h
|
pascal@24478
|
454 cmp al, '.'
|
pascal@24478
|
455 jne puts
|
pascal@24476
|
456 cbw
|
pascal@24535
|
457 int 16h ; wait for a key...
|
pascal@24535
|
458 int 19h ; bootstrap
|
pascal@24525
|
459
|
pascal@24525
|
460 Stop:
|
pascal@24525
|
461 hlt
|
pascal@24525
|
462 jmp short Stop
|
pascal@24476
|
463
|
pascal@24476
|
464 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
465 ;; Name of the file to load and run ;;
|
pascal@24476
|
466 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
467
|
pascal@24476
|
468 ProgramName db "STARTUP BIN" ; name and extension each must be
|
pascal@24476
|
469 ; padded with spaces (11 bytes total)
|
pascal@24476
|
470
|
pascal@24476
|
471 ;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
472 ;; End of the sector ID ;;
|
pascal@24476
|
473 ;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
474
|
pascal@24476
|
475 dw 0AA55h ; BIOS checks for this ID
|