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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@25569
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14 ;; - FAT12 and/or 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@25564
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29 ;; Known Limitation: ;;
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pascal@25564
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30 ;; ~~~~~~~~~~~~~~~~~ ;;
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pascal@25564
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31 ;; - Need a up to date field bpbHiddenSectors to work in a partition ; ;;
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pascal@25564
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32 ;; most formatters don't update it correcly in extended partitions. ;;
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pascal@25564
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33 ;; ;;
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pascal@25569
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34 ;; - Partition must fit in the first 8GB disk of the for CHS reads. ;;
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pascal@25569
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35 ;; (or 2TB for LBA reads). ;;
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pascal@25564
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36 ;; ;;
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pascal@25564
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37 ;; ;;
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pascal@24476
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38 ;; Known Bugs: ;;
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pascal@24476
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39 ;; ~~~~~~~~~~~ ;;
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pascal@24476
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40 ;; - 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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41 ;; on the following types of diskettes (FAT12): ;;
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pascal@24476
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42 ;; - 360KB 5"25 ;;
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pascal@24476
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43 ;; - 1.2MB 5"25 ;;
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pascal@24476
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44 ;; - 1.44MB 3"5 ;;
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pascal@24476
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45 ;; on my HDD (FAT16). ;;
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pascal@24476
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46 ;; ;;
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pascal@24476
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47 ;; ;;
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pascal@24476
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48 ;; Memory Layout: ;;
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pascal@24476
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49 ;; ~~~~~~~~~~~~~~ ;;
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pascal@24476
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50 ;; The diagram below shows the typical memory layout. The actual location ;;
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pascal@24476
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51 ;; 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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52 ;; reserves memory for its Extended BIOS Data Area just below A0000H and ;;
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pascal@24476
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53 ;; reports less than 640 KB of RAM via its Int 12H function. ;;
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pascal@24476
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54 ;; ;;
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pascal@24476
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55 ;; physical address ;;
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pascal@24476
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56 ;; +------------------------+ 00000H ;;
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pascal@24476
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57 ;; | Interrupt Vector Table | ;;
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pascal@24476
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58 ;; +------------------------+ 00400H ;;
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pascal@24476
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59 ;; | BIOS Data Area | ;;
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pascal@24476
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60 ;; +------------------------+ 00500H ;;
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pascal@24476
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61 ;; | PrtScr Status / Unused | ;;
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pascal@24476
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62 ;; +------------------------+ 00600H ;;
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pascal@24476
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63 ;; | Loaded Image | ;;
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pascal@24476
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64 ;; +------------------------+ nnnnnH ;;
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pascal@24476
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65 ;; | Available Memory | ;;
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pascal@24476
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66 ;; +------------------------+ A0000H - 512 - 3KB ;;
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pascal@24476
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67 ;; | Boot Sector | ;;
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pascal@24476
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68 ;; +------------------------+ A0000H - 3KB ;;
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pascal@24476
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69 ;; | 3KB Boot Stack | ;;
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pascal@24476
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70 ;; +------------------------+ A0000H ;;
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pascal@24476
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71 ;; | Video RAM | ;;
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pascal@24476
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72 ;; ;;
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pascal@24476
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73 ;; ;;
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pascal@24476
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74 ;; Boot Image Startup (register values): ;;
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pascal@24476
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75 ;; ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ;;
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pascal@24945
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76 ;; ax = 0ffffh (both FCB in the PSP don't have a valid drive identifier), ;;
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pascal@25454
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77 ;; bx = 0, dl = BIOS boot drive number (e.g. 0, 80H) ;;
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pascal@24476
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78 ;; cs:ip = program entry point ;;
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pascal@24476
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79 ;; ss:sp = program stack (don't confuse with boot sector's stack) ;;
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pascal@24476
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80 ;; COM program defaults: cs = ds = es = ss = 50h, sp = 0, ip = 100h ;;
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pascal@24476
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81 ;; EXE program defaults: ds = es = EXE data - 10h (fake MS-DOS psp), ;;
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pascal@24476
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82 ;; cs:ip and ss:sp depends on EXE header ;;
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pascal@24476
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83 ;; Magic numbers: ;;
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pascal@24476
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84 ;; si = 16381 (prime number 2**14-3) ;;
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pascal@24476
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85 ;; di = 32749 (prime number 2**15-19) ;;
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pascal@24476
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86 ;; bp = 65521 (prime number 2**16-15) ;;
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pascal@24476
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87 ;; The magic numbers let the program know whether it has been loaded by ;;
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pascal@24476
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88 ;; this boot sector or by MS-DOS, which may be handy for universal, bare- ;;
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pascal@24476
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89 ;; metal and MS-DOS programs. ;;
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pascal@24945
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90 ;; The command line contains no arguments. ;;
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pascal@24476
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91 ;; ;;
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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@24476
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94 %define bx(label) bx+label-boot
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pascal@25450
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95 %define si(label) si+label-boot
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pascal@25458
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96 NullEntryCheck equ 1 ; +2 bytes
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pascal@25569
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97 ReadRetry equ 1 ; +9/+13 bytes
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pascal@25569
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98 LBAsupport equ 1 ; +18 bytes
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pascal@25564
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99 CHSsanityCheck equ 1 ; +12/+16 bytes
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pascal@25569
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100 GeometryCheck equ 1 ; +20 bytes
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pascal@25564
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101 CheckAttrib equ 0 ; +6 bytes
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pascal@25564
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102 WaitForKey equ 0 ; +5 bytes
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pascal@25550
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103 SectorOf512Bytes equ 0 ; -4/-6 bytes
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pascal@25564
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104 Always2FATs equ 0 ; -1 bytes
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pascal@24476
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105
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pascal@24476
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106 [BITS 16]
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pascal@24476
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107 [CPU 8086]
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pascal@24476
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108
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pascal@24476
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109 ImageLoadSeg equ 60h
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pascal@24476
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110 StackSize equ 3072 ; Stack + cluster list
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pascal@24476
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111
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pascal@24476
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112 [SECTION .text]
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pascal@24476
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113 [ORG 0]
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pascal@24476
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114
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pascal@24476
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115 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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116 ;; Boot sector starts here ;;
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pascal@24476
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117 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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118
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pascal@24476
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119 boot:
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pascal@25450
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120 DriveNumber:
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pascal@24476
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121 jmp short start ; MS-DOS/Windows checks for this jump
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pascal@24476
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122 nop
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pascal@24476
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123 bsOemName DB "BootProg" ; 0x03
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pascal@24476
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124
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pascal@24476
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125 ;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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126 ;; BPB starts here ;;
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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@25564
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129 bpbBytesPerSector DW 0 ; 0x0B 512, 1024, 2048 or 4096
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pascal@25564
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130 bpbSectorsPerCluster DB 0 ; 0x0D 1, 2, 4, 8, 16, 32 or 64
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pascal@25564
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131 bpbReservedSectors DW 0 ; 0x0E 1
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pascal@25564
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132 bpbNumberOfFATs DB 0 ; 0x10 2
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pascal@24479
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133 bpbRootEntries DW 0 ; 0x11
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pascal@24479
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134 bpbTotalSectors DW 0 ; 0x13
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pascal@24479
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135 bpbMedia DB 0 ; 0x15
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pascal@24479
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136 bpbSectorsPerFAT DW 0 ; 0x16
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pascal@24479
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137 bpbSectorsPerTrack DW 0 ; 0x18
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pascal@24479
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138 bpbHeadsPerCylinder DW 0 ; 0x1A
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pascal@24479
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139 bpbHiddenSectors DD 0 ; 0x1C
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pascal@24479
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140 bpbTotalSectorsBig DD 0 ; 0x20
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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 ;; BPB ends here ;;
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pascal@24476
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144 ;;;;;;;;;;;;;;;;;;;
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pascal@24476
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145
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pascal@24479
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146 bsDriveNumber DB 0 ; 0x24
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pascal@24479
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147 bsUnused DB 0 ; 0x25
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pascal@25564
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148 bsExtBootSignature DB 0 ; 0x26 29
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pascal@24479
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149 bsSerialNumber DD 0 ; 0x27
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pascal@25458
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150 bsVolumeLabel times 11 DB " " ; 0x2B "NO NAME "
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pascal@25458
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151 bsFileSystem times 8 DB " " ; 0x36 "FAT12 " or "FAT16 "
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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 ;; Boot sector code starts here ;;
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pascal@24476
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155 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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156
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pascal@24476
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157 start:
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pascal@24476
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158 cld
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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 ;; How much RAM is there? ;;
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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 int 12h ; get conventional memory size (in KBs)
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pascal@24476
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165 mov cx, 106h
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pascal@24476
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166 shl ax, cl ; and convert it to 16-byte paragraphs
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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 ;; Reserve memory for the boot sector and its stack ;;
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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 sub ax, (512+StackSize) /16 ; reserve bytes for the code and the stack
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pascal@24476
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173 mov es, ax ; cs:0 = ds:0 = ss:0 -> top - 512 - StackSize
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pascal@24476
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174 mov ss, ax
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pascal@24476
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175 mov sp, 512+StackSize ; bytes 0-511 are reserved for the boot code
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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 ;; Copy ourselves to top of memory ;;
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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 mov si, 7C00h
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pascal@24476
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182 xor di, di
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pascal@24476
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183 mov ds, di
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pascal@25450
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184 push es
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pascal@25450
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185 mov [si(DriveNumber)], dx ; store BIOS boot drive number
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pascal@24476
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186 rep movsw ; move 512 bytes (+ 12)
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pascal@24476
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187
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pascal@24476
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188 ;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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189 ;; Jump to the copy ;;
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pascal@24476
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190 ;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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191
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pascal@24476
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192 mov cl, byte main
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pascal@24476
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193 push cx
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pascal@24476
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194 retf
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pascal@24476
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195
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pascal@24476
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196 main:
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pascal@24476
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197 %if ImageLoadSeg != main-boot
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pascal@24476
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198 %if ImageLoadSeg >= 100h
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pascal@24476
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199 mov cx, ImageLoadSeg
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pascal@24476
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200 %else
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pascal@24476
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201 mov cl, ImageLoadSeg
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pascal@24476
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202 %endif
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pascal@24476
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203 %endif
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pascal@24476
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204 push cx
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pascal@24476
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205
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pascal@24476
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206 ;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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207 ;; Get drive parameters ;;
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pascal@24476
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208 ;; Update heads count ;;
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pascal@24476
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209 ;; for current BIOS ;;
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pascal@24476
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210 ;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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211
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pascal@25450
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212 %if GeometryCheck != 0
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pascal@25564
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213 %if ((main-boot) & 3Fh) != 0
|
pascal@25569
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214 xor cx, cx
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pascal@25564
|
215 %endif
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pascal@25564
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216 mov ah, 8 ; update AX,BL,CX,DX,DI, and ES registers
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pascal@24476
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217 int 13h ; may destroy SI,BP, and DS registers
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pascal@25450
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218 %endif
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pascal@24476
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219 push cs
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pascal@24476
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220 pop ds
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pascal@24476
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221 xor bx, bx
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pascal@24476
|
222
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pascal@25450
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223 %if GeometryCheck != 0
|
pascal@24479
|
224 and cx, byte 3Fh
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pascal@25564
|
225 je BadParams ; verify updated and validity
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pascal@25564
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226 mov [bx(bpbSectorsPerTrack)], cx
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pascal@25564
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227 mov cl, dh
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pascal@25564
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228 inc cx
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pascal@25564
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229 mov [bx(bpbHeadsPerCylinder)], cx
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pascal@24476
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230 BadParams:
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pascal@25450
|
231 %endif
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pascal@24476
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232
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pascal@24476
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233 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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234 ;; Load FAT (FAT12: 6KB max, FAT16: 128KB max) ;;
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pascal@24476
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235 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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236
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pascal@24476
|
237 pop es ; ImageLoadSeg
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pascal@24476
|
238 push es
|
pascal@24476
|
239
|
pascal@24476
|
240 mul bx ; dx:ax = 0 = LBA (LBA are relative to FAT)
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pascal@25458
|
241 mov di, word [bx(bpbSectorsPerFAT)]
|
pascal@24476
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242
|
pascal@25458
|
243 call ReadDISectors ; read fat; clear ax, cx, di; bp = SectorsPerFAT
|
pascal@24476
|
244
|
pascal@24476
|
245 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
|
246 ;; load the root directory in ;;
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pascal@24476
|
247 ;; its entirety (16KB max) ;;
|
pascal@24476
|
248 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
|
249
|
pascal@25458
|
250 %if SectorOf512Bytes != 0
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pascal@25458
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251 mov di, word [bx(bpbRootEntries)]
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pascal@25458
|
252 mov cl, 4
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pascal@25458
|
253 shr di, cl ; di = root directory size in sectors
|
pascal@25458
|
254 %else
|
pascal@24942
|
255 mov al, 32
|
pascal@24476
|
256
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pascal@24476
|
257 mul word [bx(bpbRootEntries)]
|
pascal@24476
|
258 div word [bx(bpbBytesPerSector)]
|
pascal@25458
|
259 xchg ax, di ; di = root directory size in sectors, clear ah
|
pascal@25458
|
260 %endif
|
pascal@24476
|
261
|
pascal@25564
|
262 %if Always2FATs != 0
|
pascal@25564
|
263 mov al, 2
|
pascal@25564
|
264 %else
|
pascal@24476
|
265 mov al, [bpbNumberOfFATs]
|
pascal@25564
|
266 %endif
|
pascal@25458
|
267 mul bp ; [bx(bpbSectorsPerFAT)], set by ReadDISectors
|
pascal@24476
|
268
|
pascal@25457
|
269 push es ; read root directory
|
pascal@25458
|
270 call ReadDISectors ; clear ax, cx, di; bp = first data sector
|
pascal@24476
|
271 pop es
|
pascal@24476
|
272
|
pascal@24476
|
273 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
274 ;; Look for the COM/EXE file to load and run ;;
|
pascal@24476
|
275 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
276
|
pascal@24476
|
277 ; es:di -> root entries array
|
pascal@24476
|
278
|
pascal@24476
|
279 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
280 ;; Looks for the file/dir ProgramName ;;
|
pascal@24476
|
281 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
282 ;; Input: ES:DI -> root directory array ;;
|
pascal@24476
|
283 ;; Output: SI = cluster number ;;
|
pascal@24476
|
284 ;; AX = file sector count ;;
|
pascal@24476
|
285 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
286
|
pascal@24476
|
287 FindNameCycle:
|
pascal@24476
|
288 push di
|
pascal@25454
|
289 mov cl, NameLength
|
pascal@24476
|
290 mov si, ProgramName ; ds:si -> program name
|
pascal@24476
|
291 repe cmpsb
|
pascal@25467
|
292 %if CheckAttrib != 0
|
pascal@25467
|
293 VolumeLabel equ 8
|
pascal@25467
|
294 SubDirectory equ 10h
|
pascal@25467
|
295 jnz SkipFindName
|
pascal@25467
|
296 test byte [es:di], VolumeLabel+SubDirectory
|
pascal@25467
|
297 SkipFindName:
|
pascal@25467
|
298 %endif
|
pascal@24476
|
299 pop di
|
pascal@24476
|
300 je FindNameFound
|
pascal@25450
|
301 %if NullEntryCheck != 0
|
pascal@25564
|
302 scasb ; Z == NC
|
pascal@25458
|
303 cmc
|
pascal@25458
|
304 lea di, [di+31]
|
pascal@25458
|
305 dec word [bx(bpbRootEntries)]
|
pascal@25458
|
306 ja FindNameCycle ; next root entry
|
pascal@25450
|
307 %else
|
pascal@25450
|
308 add di, byte 32
|
pascal@24476
|
309 dec word [bx(bpbRootEntries)]
|
pascal@24476
|
310 jnz FindNameCycle ; next root entry
|
pascal@25458
|
311 %endif
|
pascal@24476
|
312
|
pascal@24476
|
313 FindNameFailed:
|
pascal@24476
|
314 call Error
|
pascal@24476
|
315 db "File not found."
|
pascal@24476
|
316
|
pascal@24476
|
317 FindNameFound:
|
pascal@24476
|
318 push si
|
pascal@24476
|
319 mov si, [es:di+1Ah] ; si = cluster no.
|
pascal@24476
|
320 les ax, [es:di+1Ch] ; file size
|
pascal@24476
|
321 mov dx, es
|
pascal@24476
|
322 div word [bx(bpbBytesPerSector)]
|
pascal@24476
|
323 cmp bx, dx ; sector aligned ?
|
pascal@24476
|
324 adc ax, bx ; file last sector
|
pascal@24476
|
325 pop di ; di = ClusterList
|
pascal@24476
|
326
|
pascal@24476
|
327 pop es ; ImageLoadSeg
|
pascal@24476
|
328 push ax
|
pascal@24476
|
329
|
pascal@24476
|
330 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
331 ;; build cluster list ;;
|
pascal@24476
|
332 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
333 ;; Input: ES:0 -> FAT ;;
|
pascal@24476
|
334 ;; SI = first cluster ;;
|
pascal@24476
|
335 ;; DI = cluster list :;
|
pascal@24476
|
336 ;; CH = 0 ;;
|
pascal@24476
|
337 ;; Output: SI = cluster list ;;
|
pascal@24476
|
338 ;; CH = 0 ;;
|
pascal@24476
|
339 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
340
|
pascal@25458
|
341 FAT12 equ 1
|
pascal@25458
|
342 FAT16 equ 1
|
pascal@25550
|
343 TINYFAT16 equ 1 ; < 4072 clusters fat16 support
|
pascal@25453
|
344 push di ; up to 2 * 635K / BytesPerCluster = 2540 bytes
|
pascal@25450
|
345 %if FAT12 == 1
|
pascal@25454
|
346 mov cl, 12
|
pascal@25564
|
347 %else
|
pascal@25564
|
348 nop
|
pascal@25564
|
349 nop
|
pascal@25450
|
350 %endif
|
pascal@24476
|
351 ClusterLoop:
|
pascal@24476
|
352 mov [di], si
|
pascal@25450
|
353 add si, si ; si = cluster * 2
|
pascal@25450
|
354 %if FAT16 == 1
|
pascal@24476
|
355 mov ax, es ; ax = FAT segment = ImageLoadSeg
|
pascal@25094
|
356 jnc First64k
|
pascal@24476
|
357 mov ah, (1000h+ImageLoadSeg)>>8 ; adjust segment for 2nd part of FAT16
|
pascal@25094
|
358 First64k:
|
pascal@25453
|
359 %if FAT12 == 1
|
pascal@25457
|
360 mov dx, 0FFF6h
|
pascal@25454
|
361 %if TINYFAT16 == 1
|
pascal@25550
|
362 test [bx(bsFileSystem+4)], cl ; FAT12 or FAT16 ? clear C (bit 2)
|
pascal@25458
|
363 jne ReadClusterFat16
|
pascal@25454
|
364 %else
|
pascal@25454
|
365 cmp [bx(bpbSectorsPerFAT)], cx ; 1..12 = FAT12, 16..256 = FAT16
|
pascal@25458
|
366 ja ReadClusterFat16
|
pascal@25454
|
367 %endif
|
pascal@24942
|
368 mov dh, 0Fh
|
pascal@25453
|
369 %endif
|
pascal@25450
|
370 %endif
|
pascal@25450
|
371 %if FAT12 == 1
|
pascal@25087
|
372 add si, [di]
|
pascal@24476
|
373 shr si, 1 ; si = cluster * 3 / 2
|
pascal@25564
|
374 %else
|
pascal@25564
|
375 nop
|
pascal@25564
|
376 nop
|
pascal@25450
|
377 %endif
|
pascal@25450
|
378 %if FAT16 == 1
|
pascal@24942
|
379 ReadClusterFat16:
|
pascal@25094
|
380 push ds
|
pascal@25087
|
381 mov ds, ax
|
pascal@24476
|
382 lodsw ; ax = next cluster
|
pascal@25094
|
383 pop ds
|
pascal@25450
|
384 %else
|
pascal@25453
|
385 es lodsw
|
pascal@25450
|
386 %endif
|
pascal@25450
|
387 %if FAT12 == 1
|
pascal@24476
|
388 jnc ReadClusterEven
|
pascal@25454
|
389 rol ax, cl
|
pascal@24476
|
390 ReadClusterEven:
|
pascal@25094
|
391 scasw ; di += 2
|
pascal@25454
|
392 %if FAT16 == 1
|
pascal@24942
|
393 and ah, dh ; mask cluster value
|
pascal@24942
|
394 cmp ax, dx
|
pascal@25454
|
395 %else
|
pascal@25453
|
396 and ah, 0Fh ; mask cluster value
|
pascal@25457
|
397 cmp ax, 0FF6h
|
pascal@25454
|
398 %endif
|
pascal@25454
|
399 %else
|
pascal@25454
|
400 scasw ; di += 2
|
pascal@25457
|
401 cmp ax, 0FFF6h
|
pascal@25453
|
402 %endif
|
pascal@24476
|
403 xchg ax, si
|
pascal@24476
|
404 jc ClusterLoop
|
pascal@24476
|
405 pop si
|
pascal@24476
|
406 pop di ; file size in sectors
|
pascal@24476
|
407
|
pascal@24476
|
408 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
409 ;; Load the entire file ;;
|
pascal@24476
|
410 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
411 ;; Input: ES:0 -> buffer ;;
|
pascal@24476
|
412 ;; SI = cluster list ;;
|
pascal@24476
|
413 ;; DI = file sectors ;;
|
pascal@24476
|
414 ;; CH = 0 ;;
|
pascal@24945
|
415 ;; BP = 1st data sec ;;
|
pascal@24476
|
416 ;; Output: BP:0 -> buffer ;;
|
pascal@24476
|
417 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
418
|
pascal@24476
|
419 push es
|
pascal@24476
|
420
|
pascal@24476
|
421 ReadClusters:
|
pascal@24476
|
422 lodsw
|
pascal@24476
|
423 dec ax
|
pascal@24476
|
424 dec ax
|
pascal@24476
|
425
|
pascal@25454
|
426 mov cl, [bx(bpbSectorsPerCluster)] ; 1..128
|
pascal@24476
|
427 mul cx ; cx = sector count (ch = 0)
|
pascal@24476
|
428
|
pascal@24476
|
429 add ax, bp ; LBA for cluster data
|
pascal@24476
|
430 adc dx, bx ; dx:ax = LBA
|
pascal@24476
|
431
|
pascal@25458
|
432 call ReadSectors ; clear ax, restore dx
|
pascal@24476
|
433
|
pascal@25458
|
434 jne ReadClusters ; until end of file
|
pascal@24476
|
435
|
pascal@24476
|
436 pop bp ; ImageLoadSeg
|
pascal@24476
|
437
|
pascal@24476
|
438 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
439 ;; Type detection, .COM or .EXE? ;;
|
pascal@24476
|
440 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
441
|
pascal@24476
|
442 mov ds, bp ; bp=ds=seg the file is loaded to
|
pascal@24476
|
443
|
pascal@24476
|
444 add bp, [bx+08h] ; bp = image base
|
pascal@24476
|
445 mov di, [bx+18h] ; di = reloc table pointer
|
pascal@24476
|
446
|
pascal@24476
|
447 cmp word [bx], 5A4Dh ; "MZ" signature?
|
pascal@24476
|
448 je RelocateEXE ; yes, it's an EXE program
|
pascal@24476
|
449
|
pascal@24476
|
450 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
451 ;; Setup and run a .COM program ;;
|
pascal@24476
|
452 ;; Set CS=DS=ES=SS SP=0 IP=100h ;;
|
pascal@25454
|
453 ;; AX=0ffffh BX=0 DX=drive and ;;
|
pascal@25454
|
454 ;; cmdline=void ;;
|
pascal@24476
|
455 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
456
|
pascal@24942
|
457 mov di, 100h ; ip
|
pascal@24476
|
458 mov bp, ImageLoadSeg-10h ; "org 100h" stuff :)
|
pascal@24476
|
459 mov ss, bp
|
pascal@24476
|
460 xor sp, sp
|
pascal@24476
|
461 push bp ; cs, ds and es
|
pascal@24476
|
462 jmp short Run
|
pascal@24476
|
463
|
pascal@24476
|
464 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
465 ;; Relocate, setup and run a .EXE program ;;
|
pascal@24476
|
466 ;; Set CS:IP, SS:SP, DS, ES and AX according ;;
|
pascal@24476
|
467 ;; to wiki.osdev.org/MZ#Initial_Program_State ;;
|
pascal@25454
|
468 ;; AX=0ffffh BX=0 DX=drive cmdline=void ;;
|
pascal@24476
|
469 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
470
|
pascal@24476
|
471 ReloCycle:
|
pascal@24476
|
472 add [di+2], bp ; item seg (abs)
|
pascal@24476
|
473 les si, [di] ; si = item ofs, es = item seg
|
pascal@24476
|
474 add [es:si], bp ; fixup
|
pascal@24476
|
475 scasw ; di += 2
|
pascal@24476
|
476 scasw ; point to next entry
|
pascal@24476
|
477
|
pascal@24476
|
478 RelocateEXE:
|
pascal@24942
|
479 dec word [bx+06h] ; reloc items, 32768 max (128KB table)
|
pascal@24942
|
480 jns ReloCycle
|
pascal@24476
|
481 ; PSP don't have a valid drive identifier
|
pascal@24476
|
482 les si, [bx+0Eh]
|
pascal@24476
|
483 add si, bp
|
pascal@24476
|
484 mov ss, si ; ss for EXE
|
pascal@24476
|
485 mov sp, es ; sp for EXE
|
pascal@24476
|
486
|
pascal@24476
|
487 lea si, [bp-10h] ; ds and es both point to the segment
|
pascal@24476
|
488 push si ; containing the PSP structure
|
pascal@24476
|
489
|
pascal@24476
|
490 add bp, [bx+16h] ; cs for EXE
|
pascal@24942
|
491 mov di, [bx+14h] ; ip for EXE
|
pascal@24476
|
492 Run:
|
pascal@24476
|
493 pop ds
|
pascal@24476
|
494 push bp
|
pascal@24942
|
495 push di
|
pascal@24476
|
496 push ds
|
pascal@24476
|
497 pop es
|
pascal@24942
|
498 mov [80h], ax ; clear cmdline
|
pascal@24942
|
499 dec ax ; both FCB in the PSP don't have a valid drive identifier
|
pascal@24476
|
500
|
pascal@24476
|
501 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
502 ;; Set the magic numbers so the program knows that it ;;
|
pascal@24476
|
503 ;; has been loaded by this bootsector and not by MS-DOS ;;
|
pascal@24476
|
504 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
505 mov si, 16381 ; prime number 2**14-3
|
pascal@24476
|
506 mov di, 32749 ; prime number 2**15-19
|
pascal@24476
|
507 mov bp, 65521 ; prime number 2**16-15
|
pascal@24476
|
508
|
pascal@24476
|
509 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
510 ;; All done, transfer control to the program now ;;
|
pascal@24476
|
511 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
512 retf
|
pascal@24476
|
513
|
pascal@25458
|
514 ;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@25458
|
515 ;; Error Messaging Code ;;
|
pascal@25458
|
516 ;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@25458
|
517
|
pascal@25458
|
518 Error:
|
pascal@25458
|
519 pop si
|
pascal@25458
|
520
|
pascal@25458
|
521 PutStr:
|
pascal@25458
|
522 mov ah, 0Eh
|
pascal@25458
|
523 mov bl, 7
|
pascal@25458
|
524 lodsb
|
pascal@25458
|
525 int 10h
|
pascal@25458
|
526 cmp al, "."
|
pascal@25458
|
527 jne PutStr
|
pascal@25564
|
528 %if WaitForKey != 0
|
pascal@25458
|
529 cbw
|
pascal@25458
|
530 int 16h ; wait for a key...
|
pascal@25458
|
531 int 19h ; bootstrap
|
pascal@25564
|
532 %endif
|
pascal@25458
|
533 Stop:
|
pascal@25458
|
534 hlt
|
pascal@25458
|
535 jmp short Stop
|
pascal@25458
|
536
|
pascal@25458
|
537 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@25458
|
538 ;; Read sectors using BIOS Int 13h ;;
|
pascal@25458
|
539 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@25458
|
540 ;; Input: DX:AX = LBA relative to FAT ;;
|
pascal@25458
|
541 ;; BX = 0 ;;
|
pascal@25458
|
542 ;; DI = sector count ;;
|
pascal@25458
|
543 ;; ES:BX -> buffer address ;;
|
pascal@25458
|
544 ;; Output: ES:BX -> next address ;;
|
pascal@25458
|
545 ;; BX = 0 ;;
|
pascal@25458
|
546 ;; CX = 0 ;;
|
pascal@25458
|
547 ;; DI = 0 ;;
|
pascal@25458
|
548 ;; DL = drive number ;;
|
pascal@25564
|
549 ;; 0:BP = next LBA from FAT ;;
|
pascal@25458
|
550 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@25458
|
551
|
pascal@25458
|
552 ReadDISectors:
|
pascal@25458
|
553 mov bp, di
|
pascal@24476
|
554 add bp, ax ; adjust LBA for cluster data
|
pascal@24476
|
555
|
pascal@25458
|
556 mov cx, di ; no cluster size limit
|
pascal@24476
|
557
|
pascal@24476
|
558 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@25458
|
559 ;; Read sectors using BIOS Int 13h ;;
|
pascal@24476
|
560 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
561 ;; Input: DX:AX = LBA relative to FAT ;;
|
pascal@24476
|
562 ;; BX = 0 ;;
|
pascal@24476
|
563 ;; CX = sector count ;;
|
pascal@24476
|
564 ;; DI = file sectors ;;
|
pascal@24476
|
565 ;; ES:BX -> buffer address ;;
|
pascal@24476
|
566 ;; Output: ES:BX -> next address ;;
|
pascal@24476
|
567 ;; BX = 0 ;;
|
pascal@24476
|
568 ;; CX or DI = 0 ;;
|
pascal@24476
|
569 ;; DL = drive number ;;
|
pascal@25564
|
570 ;; Keep: BP, SI ;;
|
pascal@24476
|
571 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
572
|
pascal@25458
|
573 ReadSectors:
|
pascal@24476
|
574 add ax, [bx(bpbHiddenSectors)]
|
pascal@24476
|
575 adc dx, [bx(bpbHiddenSectors)+2]
|
pascal@24476
|
576 add ax, [bx(bpbReservedSectors)]
|
pascal@24476
|
577
|
pascal@24476
|
578 push si
|
pascal@24476
|
579 ReadSectorNext:
|
pascal@24476
|
580 adc dx, bx
|
pascal@24476
|
581 push di
|
pascal@24476
|
582 push cx
|
pascal@24476
|
583
|
pascal@25450
|
584 %if LBAsupport != 0
|
pascal@24476
|
585 push bx
|
pascal@24476
|
586 push bx
|
pascal@25450
|
587 %endif
|
pascal@24476
|
588 push dx ; 32-bit LBA: up to 2TB
|
pascal@24476
|
589 push ax
|
pascal@24476
|
590 push es
|
pascal@25450
|
591 %if ReadRetry != 0 || LBAsupport != 0
|
pascal@25450
|
592 mov di, 16 ; packet size byte = 16, reserved byte = 0
|
pascal@25450
|
593 %endif
|
pascal@25450
|
594 %if LBAsupport != 0
|
pascal@24476
|
595 push bx
|
pascal@24476
|
596 inc bx ; sector count word = 1
|
pascal@24476
|
597 push bx
|
pascal@24476
|
598 dec bx
|
pascal@24476
|
599 push di
|
pascal@25450
|
600 %endif
|
pascal@25569
|
601 mov si, sp
|
pascal@24476
|
602
|
pascal@24476
|
603 xchg ax, cx ; save low LBA
|
pascal@24476
|
604 xchg ax, dx ; get high LBA
|
pascal@25452
|
605 cwd ; clear dx (LBA offset <1TB)
|
pascal@25450
|
606 idiv word [bx(bpbSectorsPerTrack)] ; up to 8GB disks
|
pascal@24476
|
607
|
pascal@25569
|
608 %if CHSsanityCheck != 0
|
pascal@25564
|
609 inc ax
|
pascal@25564
|
610 cmp ax, [bx(bpbHeadsPerCylinder)]
|
pascal@25564
|
611 ja CHSoverflow
|
pascal@25564
|
612 dec ax
|
pascal@25569
|
613 %endif
|
pascal@24476
|
614 xchg ax, cx ; restore low LBA, save high LBA / SPT
|
pascal@25450
|
615 idiv word [bx(bpbSectorsPerTrack)]
|
pascal@24476
|
616 ; ax = LBA / SPT
|
pascal@24476
|
617 ; dx = LBA % SPT = sector - 1
|
pascal@24476
|
618 inc dx
|
pascal@24476
|
619
|
pascal@24476
|
620 xchg cx, dx ; restore high LBA / SPT, save sector no.
|
pascal@25564
|
621 idiv word [bx(bpbHeadsPerCylinder)] ; may overflow if SectorsPerTrack * HeadsPerCylinder < 256 or disk > 8GB
|
pascal@24476
|
622 ; ax = (LBA / SPT) / HPC = cylinder
|
pascal@24476
|
623 ; dx = (LBA / SPT) % HPC = head
|
pascal@25458
|
624
|
pascal@25458
|
625 xchg ch, al ; clear al
|
pascal@24476
|
626 ; ch = LSB 0...7 of cylinder no.
|
pascal@25458
|
627 shr ax, 1
|
pascal@25458
|
628 shr ax, 1
|
pascal@24476
|
629 or cl, al
|
pascal@24476
|
630 ; cl = MSB 8...9 of cylinder no. + sector no.
|
pascal@24476
|
631 mov dh, dl
|
pascal@24476
|
632 ; dh = head no.
|
pascal@24476
|
633
|
pascal@25564
|
634 %if CHSsanityCheck != 0
|
pascal@25564
|
635 %if LBAsupport != 0
|
pascal@25564
|
636 or ah, [si+8+3] ; 8GB max, last cylinder 1023
|
pascal@25564
|
637 %else
|
pascal@25564
|
638 or ah, [si+2+3] ; 8GB max, last cylinder 1023
|
pascal@25564
|
639 %endif
|
pascal@25564
|
640 %endif
|
pascal@25564
|
641 CHSoverflow:
|
pascal@25569
|
642 %if CHSsanityCheck != 0 && (ReadRetry != 0 || LBAsupport != 0)
|
pascal@25564
|
643 pushf
|
pascal@25564
|
644 %endif
|
pascal@25564
|
645
|
pascal@25564
|
646 ReadSectorRetry:
|
pascal@25569
|
647 mov dl, [bx(DriveNumber)]
|
pascal@25569
|
648 ; dl = drive no.
|
pascal@25450
|
649 %if LBAsupport != 0
|
pascal@24476
|
650 mov ah, 42h ; ah = 42h = extended read function no.
|
pascal@24476
|
651 int 13h ; extended read sectors (DL, DS:SI)
|
pascal@24476
|
652 jnc ReadSectorNextSegment
|
pascal@25450
|
653 %endif
|
pascal@25564
|
654 %if CHSsanityCheck != 0
|
pascal@25564
|
655 %if ReadRetry != 0 || LBAsupport != 0
|
pascal@25564
|
656 popf
|
pascal@25564
|
657 pushf
|
pascal@25564
|
658 %endif
|
pascal@25564
|
659 jne SkipCHS
|
pascal@25564
|
660 %endif
|
pascal@24476
|
661
|
pascal@24476
|
662 mov ax, 201h ; al = sector count = 1
|
pascal@24476
|
663 ; ah = 2 = read function no.
|
pascal@24476
|
664 int 13h ; read sectors (AL, CX, DX, ES:BX)
|
pascal@24476
|
665
|
pascal@24476
|
666 jnc ReadSectorNextSegment
|
pascal@25564
|
667 SkipCHS:
|
pascal@25450
|
668 %if ReadRetry != 0
|
pascal@24476
|
669 cbw ; ah = 0 = reset function
|
pascal@24476
|
670 int 13h ; reset drive (DL)
|
pascal@24476
|
671
|
pascal@24476
|
672 dec di
|
pascal@25457
|
673 jnz ReadSectorRetry ; up to 15 extra attempt
|
pascal@25450
|
674 %endif
|
pascal@24476
|
675
|
pascal@25564
|
676 ReadError:
|
pascal@24476
|
677 call Error
|
pascal@24476
|
678 db "Read error."
|
pascal@24476
|
679
|
pascal@24476
|
680 ReadSectorNextSegment:
|
pascal@25564
|
681 %if CHSsanityCheck != 0 && (ReadRetry != 0 || LBAsupport != 0)
|
pascal@25564
|
682 popf
|
pascal@25564
|
683 %endif
|
pascal@25564
|
684
|
pascal@25564
|
685 %macro adjust_es 2
|
pascal@25564
|
686 %if SectorOf512Bytes != 0
|
pascal@25564
|
687 add word %1, byte 32 ; adjust segment for next sector
|
pascal@25564
|
688 %else
|
pascal@25564
|
689 %if %2 != 0
|
pascal@25564
|
690 mov al, %2
|
pascal@25564
|
691 %endif
|
pascal@25564
|
692 mul byte [bx(bpbBytesPerSector)+1] ; = (bpbBytesPerSector/256)*16
|
pascal@25564
|
693 add %1, ax ; adjust segment for next sector
|
pascal@25564
|
694 %endif
|
pascal@25564
|
695 %endmacro
|
pascal@24476
|
696
|
pascal@25450
|
697 %if LBAsupport != 0
|
pascal@24476
|
698 pop ax ; al = 16
|
pascal@25564
|
699 adjust_es [si+6], 0
|
pascal@24476
|
700 pop cx ; sector count = 1
|
pascal@24476
|
701 pop bx
|
pascal@25450
|
702 %else
|
pascal@25564
|
703 adjust_es [si], 16
|
pascal@25450
|
704 %endif
|
pascal@24476
|
705 pop es ; es:0 updated
|
pascal@24476
|
706 pop ax
|
pascal@24476
|
707 pop dx
|
pascal@25450
|
708 %if LBAsupport != 0
|
pascal@24476
|
709 pop di
|
pascal@24476
|
710 pop di
|
pascal@24476
|
711 add ax, cx ; adjust LBA for next sector
|
pascal@25450
|
712 %else
|
pascal@25450
|
713 add ax, 1 ; adjust LBA for next sector
|
pascal@25450
|
714 %endif
|
pascal@24476
|
715
|
pascal@24476
|
716 pop cx ; cluster sectors to read
|
pascal@24476
|
717 pop di ; file sectors to read
|
pascal@24476
|
718 dec di ; keep C
|
pascal@25457
|
719 loopne ReadSectorNext ; until cluster sector count or file sector count
|
pascal@24476
|
720 pop si
|
pascal@24942
|
721 mov ax, bx ; clear ax
|
pascal@25450
|
722 mov dx, [bx(DriveNumber)] ; pass the BIOS boot drive to Run or Error
|
pascal@24476
|
723
|
pascal@24476
|
724 ret
|
pascal@24476
|
725
|
pascal@24942
|
726 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24942
|
727 ;; Fill free space with zeroes ;;
|
pascal@24942
|
728 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24942
|
729
|
pascal@25458
|
730 times (512-13-($-$$)) db 0
|
pascal@24476
|
731
|
pascal@24476
|
732 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
733 ;; Name of the file to load and run ;;
|
pascal@24476
|
734 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
735
|
pascal@25463
|
736 NameLength equ 11
|
pascal@25463
|
737 ProgramName times NameLength db 0 ; name and extension
|
pascal@24476
|
738
|
pascal@24476
|
739 ;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
740 ;; End of the sector ID ;;
|
pascal@24476
|
741 ;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
742
|
pascal@24476
|
743 ClusterList dw 0AA55h ; BIOS checks for this ID
|