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pascal@24476
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1 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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2 ;; ;;
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pascal@24476
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3 ;; "BootProg" Loader v 1.5 by Alexey Frunze (c) 2000-2015 ;;
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pascal@24476
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4 ;; 2-clause BSD license. ;;
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pascal@24476
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5 ;; ;;
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pascal@24476
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6 ;; ;;
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pascal@24476
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7 ;; How to Compile: ;;
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pascal@24476
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8 ;; ~~~~~~~~~~~~~~~ ;;
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pascal@24476
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9 ;; nasm boot16.asm -f bin -o boot16.bin ;;
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pascal@24476
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10 ;; ;;
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pascal@24476
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11 ;; ;;
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pascal@24476
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12 ;; Features: ;;
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pascal@24476
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13 ;; ~~~~~~~~~ ;;
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pascal@24476
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14 ;; - FAT12 and FAT16 supported using BIOS int 13h function 42h or 02h. ;;
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pascal@24476
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15 ;; ;;
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pascal@24476
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16 ;; - Loads a 16-bit executable file in the MS-DOS .COM or .EXE format ;;
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pascal@24476
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17 ;; from the root directory of a disk and transfers control to it ;;
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pascal@24476
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18 ;; (the "ProgramName" variable holds the name of the file to be loaded) ;;
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pascal@24476
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19 ;; Its maximum size can be up to 635KB without Extended BIOS Data area. ;;
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pascal@24476
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20 ;; ;;
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pascal@24476
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21 ;; - Prints an error if the file isn't found or couldn't be read ;;
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pascal@24476
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22 ;; ("File not found" or "Read error") ;;
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pascal@24476
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23 ;; and waits for a key to be pressed, then executes the Int 19h ;;
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pascal@24476
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24 ;; instruction and lets the BIOS continue bootstrap. ;;
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pascal@24476
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25 ;; ;;
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pascal@24476
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26 ;; - cpu 8086 is supported ;;
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pascal@24476
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27 ;; ;;
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pascal@24476
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28 ;; ;;
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pascal@24476
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29 ;; Known Bugs: ;;
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pascal@24476
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30 ;; ~~~~~~~~~~~ ;;
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pascal@24476
|
31 ;; - 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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32 ;; on the following types of diskettes (FAT12): ;;
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pascal@24476
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33 ;; - 360KB 5"25 ;;
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pascal@24476
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34 ;; - 1.2MB 5"25 ;;
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pascal@24476
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35 ;; - 1.44MB 3"5 ;;
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pascal@24476
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36 ;; on my HDD (FAT16). ;;
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pascal@24476
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37 ;; ;;
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pascal@24476
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38 ;; ;;
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pascal@24476
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39 ;; Memory Layout: ;;
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pascal@24476
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40 ;; ~~~~~~~~~~~~~~ ;;
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pascal@24476
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41 ;; The diagram below shows the typical memory layout. The actual location ;;
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pascal@24476
|
42 ;; 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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43 ;; reserves memory for its Extended BIOS Data Area just below A0000H and ;;
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pascal@24476
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44 ;; reports less than 640 KB of RAM via its Int 12H function. ;;
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pascal@24476
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45 ;; ;;
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pascal@24476
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46 ;; physical address ;;
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pascal@24476
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47 ;; +------------------------+ 00000H ;;
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pascal@24476
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48 ;; | Interrupt Vector Table | ;;
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pascal@24476
|
49 ;; +------------------------+ 00400H ;;
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pascal@24476
|
50 ;; | BIOS Data Area | ;;
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pascal@24476
|
51 ;; +------------------------+ 00500H ;;
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pascal@24476
|
52 ;; | PrtScr Status / Unused | ;;
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pascal@24476
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53 ;; +------------------------+ 00600H ;;
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pascal@24476
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54 ;; | Loaded Image | ;;
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pascal@24476
|
55 ;; +------------------------+ nnnnnH ;;
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pascal@24476
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56 ;; | Available Memory | ;;
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pascal@24476
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57 ;; +------------------------+ A0000H - 512 - 3KB ;;
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pascal@24476
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58 ;; | Boot Sector | ;;
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pascal@24476
|
59 ;; +------------------------+ A0000H - 3KB ;;
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pascal@24476
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60 ;; | 3KB Boot Stack | ;;
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pascal@24476
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61 ;; +------------------------+ A0000H ;;
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pascal@24476
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62 ;; | Video RAM | ;;
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pascal@24476
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63 ;; ;;
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pascal@24476
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64 ;; ;;
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pascal@24476
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65 ;; Boot Image Startup (register values): ;;
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pascal@24476
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66 ;; ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ;;
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pascal@24945
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67 ;; ax = 0ffffh (both FCB in the PSP don't have a valid drive identifier), ;;
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pascal@25454
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68 ;; bx = 0, dl = BIOS boot drive number (e.g. 0, 80H) ;;
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pascal@24476
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69 ;; cs:ip = program entry point ;;
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pascal@24476
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70 ;; ss:sp = program stack (don't confuse with boot sector's stack) ;;
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pascal@24476
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71 ;; COM program defaults: cs = ds = es = ss = 50h, sp = 0, ip = 100h ;;
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pascal@24476
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72 ;; EXE program defaults: ds = es = EXE data - 10h (fake MS-DOS psp), ;;
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pascal@24476
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73 ;; cs:ip and ss:sp depends on EXE header ;;
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pascal@24476
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74 ;; Magic numbers: ;;
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pascal@24476
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75 ;; si = 16381 (prime number 2**14-3) ;;
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pascal@24476
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76 ;; di = 32749 (prime number 2**15-19) ;;
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pascal@24476
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77 ;; bp = 65521 (prime number 2**16-15) ;;
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pascal@24476
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78 ;; The magic numbers let the program know whether it has been loaded by ;;
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pascal@24476
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79 ;; this boot sector or by MS-DOS, which may be handy for universal, bare- ;;
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pascal@24476
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80 ;; metal and MS-DOS programs. ;;
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pascal@24945
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81 ;; The command line contains no arguments. ;;
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pascal@24476
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82 ;; ;;
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pascal@24476
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83 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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84
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pascal@24476
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85 %define bx(label) bx+label-boot
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pascal@25450
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86 %define si(label) si+label-boot
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pascal@25450
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87 NullEntryCheck equ 1 ; +3 bytes
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pascal@25450
|
88 ReadRetry equ 1 ; +9 bytes
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pascal@25450
|
89 LBAsupport equ 1 ; +16 bytes
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pascal@25450
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90 Over2GB equ 1 ; +5 bytes
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pascal@25450
|
91 GeometryCheck equ 1 ; +18 bytes
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pascal@24476
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92
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pascal@24476
|
93 [BITS 16]
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pascal@24476
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94 [CPU 8086]
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pascal@24476
|
95
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pascal@24476
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96 ImageLoadSeg equ 60h
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pascal@24476
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97 StackSize equ 3072 ; Stack + cluster list
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pascal@24476
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98
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pascal@24476
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99 [SECTION .text]
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pascal@24476
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100 [ORG 0]
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pascal@24476
|
101
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pascal@24476
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102 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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103 ;; Boot sector starts here ;;
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pascal@24476
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104 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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105
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pascal@24476
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106 boot:
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pascal@25450
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107 DriveNumber:
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pascal@24476
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108 jmp short start ; MS-DOS/Windows checks for this jump
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pascal@24476
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109 nop
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pascal@24476
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110 bsOemName DB "BootProg" ; 0x03
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pascal@24476
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111
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pascal@24476
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112 ;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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113 ;; BPB starts here ;;
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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@24479
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116 bpbBytesPerSector DW 0 ; 0x0B
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pascal@24479
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117 bpbSectorsPerCluster DB 0 ; 0x0D
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pascal@24479
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118 bpbReservedSectors DW 0 ; 0x0E
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pascal@24479
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119 bpbNumberOfFATs DB 0 ; 0x10
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pascal@24479
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120 bpbRootEntries DW 0 ; 0x11
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pascal@24479
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121 bpbTotalSectors DW 0 ; 0x13
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pascal@24479
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122 bpbMedia DB 0 ; 0x15
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pascal@24479
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123 bpbSectorsPerFAT DW 0 ; 0x16
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pascal@24479
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124 bpbSectorsPerTrack DW 0 ; 0x18
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pascal@24479
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125 bpbHeadsPerCylinder DW 0 ; 0x1A
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pascal@24479
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126 bpbHiddenSectors DD 0 ; 0x1C
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pascal@24479
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127 bpbTotalSectorsBig DD 0 ; 0x20
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pascal@24476
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128
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pascal@24476
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129 ;;;;;;;;;;;;;;;;;;;
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pascal@24476
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130 ;; BPB ends here ;;
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pascal@24476
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131 ;;;;;;;;;;;;;;;;;;;
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pascal@24476
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132
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pascal@24479
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133 bsDriveNumber DB 0 ; 0x24
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pascal@24479
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134 bsUnused DB 0 ; 0x25
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pascal@24479
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135 bsExtBootSignature DB 0 ; 0x26
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pascal@24479
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136 bsSerialNumber DD 0 ; 0x27
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pascal@24476
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137 bsVolumeLabel DB "NO NAME " ; 0x2B
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pascal@24476
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138 bsFileSystem DB "FAT12 " ; 0x36
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pascal@24476
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139
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pascal@24476
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140 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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141 ;; Boot sector code starts here ;;
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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 start:
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pascal@24476
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145 cld
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pascal@24476
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146
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pascal@24476
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147 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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148 ;; How much RAM is there? ;;
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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 int 12h ; get conventional memory size (in KBs)
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pascal@24476
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152 mov cx, 106h
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pascal@24476
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153 shl ax, cl ; and convert it to 16-byte paragraphs
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pascal@24476
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154
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pascal@24476
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155 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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156 ;; Reserve memory for the boot sector and its stack ;;
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pascal@24476
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157 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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158
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pascal@24476
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159 sub ax, (512+StackSize) /16 ; reserve bytes for the code and the stack
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pascal@24476
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160 mov es, ax ; cs:0 = ds:0 = ss:0 -> top - 512 - StackSize
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pascal@24476
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161 mov ss, ax
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pascal@24476
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162 mov sp, 512+StackSize ; bytes 0-511 are reserved for the boot code
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pascal@24476
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163
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pascal@24476
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164 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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165 ;; Copy ourselves to top of memory ;;
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pascal@24476
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166 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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167
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pascal@24476
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168 mov si, 7C00h
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pascal@24476
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169 xor di, di
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pascal@24476
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170 mov ds, di
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pascal@25450
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171 push es
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pascal@25450
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172 mov [si(DriveNumber)], dx ; store BIOS boot drive number
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pascal@24476
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173 rep movsw ; move 512 bytes (+ 12)
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pascal@24476
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174
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pascal@24476
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175 ;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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176 ;; Jump to the copy ;;
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pascal@24476
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177 ;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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178
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pascal@24476
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179 mov cl, byte main
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pascal@24476
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180 push cx
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pascal@24476
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181 retf
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pascal@24476
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182
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pascal@24476
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183 main:
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pascal@24476
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184 %if ImageLoadSeg != main-boot
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pascal@24476
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185 %if ImageLoadSeg >= 100h
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pascal@24476
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186 mov cx, ImageLoadSeg
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pascal@24476
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187 %else
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pascal@24476
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188 mov cl, ImageLoadSeg
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pascal@24476
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189 %endif
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pascal@24476
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190 %endif
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pascal@24476
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191 push cx
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pascal@24476
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192
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pascal@24476
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193 ;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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194 ;; Get drive parameters ;;
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pascal@24476
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195 ;; Update heads count ;;
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pascal@24476
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196 ;; for current BIOS ;;
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pascal@24476
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197 ;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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198
|
pascal@25450
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199 %if GeometryCheck != 0
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pascal@24476
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200 mov ah, 8
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pascal@24476
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201 int 13h ; may destroy SI,BP, and DS registers
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pascal@25450
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202 %endif
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pascal@24476
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203 ; update AX,BL,CX,DX,DI, and ES registers
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pascal@24476
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204 push cs
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pascal@24476
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205 pop ds
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pascal@24476
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206 xor bx, bx
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pascal@24476
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207
|
pascal@25450
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208 %if GeometryCheck != 0
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pascal@24479
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209 and cx, byte 3Fh
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pascal@24476
|
210 cmp [bx(bpbSectorsPerTrack)], cx
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pascal@24476
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211 jne BadParams ; verify updated and validity
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pascal@24476
|
212 mov al, dh
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pascal@24476
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213 inc ax
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pascal@24476
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214 mov [bpbHeadsPerCylinder], ax
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pascal@24476
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215 BadParams:
|
pascal@25450
|
216 %endif
|
pascal@24476
|
217
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pascal@24476
|
218 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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219 ;; Load FAT (FAT12: 6KB max, FAT16: 128KB max) ;;
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pascal@24476
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220 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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221
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pascal@24476
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222 pop es ; ImageLoadSeg
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pascal@24476
|
223 push es
|
pascal@24476
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224
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pascal@24476
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225 mul bx ; dx:ax = 0 = LBA (LBA are relative to FAT)
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pascal@24476
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226 mov cx, word [bx(bpbSectorsPerFAT)]
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pascal@24476
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227
|
pascal@24945
|
228 call ReadCXSectors ; read fat and clear ax & cx; bp = SectorsPerFAT
|
pascal@24476
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229
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pascal@24476
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230 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
|
231 ;; load the root directory in ;;
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pascal@24476
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232 ;; its entirety (16KB max) ;;
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pascal@24476
|
233 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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234
|
pascal@24942
|
235 mov al, 32
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pascal@24476
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236
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pascal@24476
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237 mul word [bx(bpbRootEntries)]
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pascal@24476
|
238 div word [bx(bpbBytesPerSector)]
|
pascal@24476
|
239 xchg ax, cx ; cx = root directory size in sectors, clear ax
|
pascal@24476
|
240
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pascal@24476
|
241 mov al, [bpbNumberOfFATs]
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pascal@24476
|
242 mul bp ; [bx(bpbSectorsPerFAT)], set by ReadCXSectors
|
pascal@24476
|
243
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pascal@24476
|
244 push es
|
pascal@24945
|
245 call ReadCXSectors ; read root directory; clear ax, cx & di; bp = first data sector
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pascal@24476
|
246 pop es
|
pascal@24476
|
247
|
pascal@24476
|
248 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
|
249 ;; Look for the COM/EXE file to load and run ;;
|
pascal@24476
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250 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
251
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pascal@24476
|
252 ; es:di -> root entries array
|
pascal@24476
|
253
|
pascal@24476
|
254 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
255 ;; Looks for the file/dir ProgramName ;;
|
pascal@24476
|
256 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
257 ;; Input: ES:DI -> root directory array ;;
|
pascal@24476
|
258 ;; Output: SI = cluster number ;;
|
pascal@24476
|
259 ;; AX = file sector count ;;
|
pascal@24476
|
260 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
261
|
pascal@24476
|
262 FindNameCycle:
|
pascal@24476
|
263 push di
|
pascal@25454
|
264 mov cl, NameLength
|
pascal@24476
|
265 mov si, ProgramName ; ds:si -> program name
|
pascal@24476
|
266 repe cmpsb
|
pascal@24476
|
267 pop di
|
pascal@24476
|
268 je FindNameFound
|
pascal@25450
|
269 %if NullEntryCheck != 0
|
pascal@24942
|
270 scasb
|
pascal@24942
|
271 je FindNameFailed ; end of root directory (NULL entry found)
|
pascal@24942
|
272 add di, byte 31
|
pascal@25450
|
273 %else
|
pascal@25450
|
274 add di, byte 32
|
pascal@25450
|
275 %endif
|
pascal@24476
|
276 dec word [bx(bpbRootEntries)]
|
pascal@24476
|
277 jnz FindNameCycle ; next root entry
|
pascal@24476
|
278
|
pascal@24476
|
279 FindNameFailed:
|
pascal@24476
|
280 call Error
|
pascal@24476
|
281 db "File not found."
|
pascal@24476
|
282
|
pascal@24476
|
283 FindNameFound:
|
pascal@24476
|
284 push si
|
pascal@24476
|
285 mov si, [es:di+1Ah] ; si = cluster no.
|
pascal@24476
|
286 les ax, [es:di+1Ch] ; file size
|
pascal@24476
|
287 mov dx, es
|
pascal@24476
|
288 div word [bx(bpbBytesPerSector)]
|
pascal@24476
|
289 cmp bx, dx ; sector aligned ?
|
pascal@24476
|
290 adc ax, bx ; file last sector
|
pascal@24476
|
291 pop di ; di = ClusterList
|
pascal@24476
|
292
|
pascal@24476
|
293 pop es ; ImageLoadSeg
|
pascal@24476
|
294 push ax
|
pascal@24476
|
295
|
pascal@24476
|
296 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
297 ;; build cluster list ;;
|
pascal@24476
|
298 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
299 ;; Input: ES:0 -> FAT ;;
|
pascal@24476
|
300 ;; SI = first cluster ;;
|
pascal@24476
|
301 ;; DI = cluster list :;
|
pascal@24476
|
302 ;; CH = 0 ;;
|
pascal@24476
|
303 ;; Output: SI = cluster list ;;
|
pascal@24476
|
304 ;; CH = 0 ;;
|
pascal@24476
|
305 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
306
|
pascal@25450
|
307 FAT12 equ 1
|
pascal@25450
|
308 FAT16 equ 1
|
pascal@25454
|
309 TINYFAT16 equ 1
|
pascal@25453
|
310 push di ; up to 2 * 635K / BytesPerCluster = 2540 bytes
|
pascal@25450
|
311 %if FAT12 == 1
|
pascal@25454
|
312 %if TINYFAT16 == 0 && FAT16 == 1
|
pascal@25454
|
313 mov cl, 12
|
pascal@25454
|
314 %else
|
pascal@25453
|
315 mov cl, 4
|
pascal@25454
|
316 %endif
|
pascal@25450
|
317 %endif
|
pascal@24476
|
318 ClusterLoop:
|
pascal@24476
|
319 mov [di], si
|
pascal@25450
|
320 add si, si ; si = cluster * 2
|
pascal@25450
|
321 %if FAT16 == 1
|
pascal@24476
|
322 mov ax, es ; ax = FAT segment = ImageLoadSeg
|
pascal@25094
|
323 jnc First64k
|
pascal@24476
|
324 mov ah, (1000h+ImageLoadSeg)>>8 ; adjust segment for 2nd part of FAT16
|
pascal@25094
|
325 First64k:
|
pascal@25453
|
326 %if FAT12 == 1
|
pascal@24942
|
327 mov dx, 0FFF8h
|
pascal@25454
|
328 %if TINYFAT16 == 1
|
pascal@25453
|
329 test [bx(bsFileSystem+4)], cl ; FAT12 or FAT16 ? clear C
|
pascal@25454
|
330 %else
|
pascal@25454
|
331 cmp [bx(bpbSectorsPerFAT)], cx ; 1..12 = FAT12, 16..256 = FAT16
|
pascal@25454
|
332 %endif
|
pascal@25453
|
333 jne ReadClusterFat16
|
pascal@24942
|
334 mov dh, 0Fh
|
pascal@25453
|
335 %endif
|
pascal@25450
|
336 %endif
|
pascal@25450
|
337 %if FAT12 == 1
|
pascal@25087
|
338 add si, [di]
|
pascal@24476
|
339 shr si, 1 ; si = cluster * 3 / 2
|
pascal@25450
|
340 %endif
|
pascal@25450
|
341 %if FAT16 == 1
|
pascal@24942
|
342 ReadClusterFat16:
|
pascal@25094
|
343 push ds
|
pascal@25087
|
344 mov ds, ax
|
pascal@24476
|
345 lodsw ; ax = next cluster
|
pascal@25094
|
346 pop ds
|
pascal@25450
|
347 %else
|
pascal@25453
|
348 es lodsw
|
pascal@25450
|
349 %endif
|
pascal@25450
|
350 %if FAT12 == 1
|
pascal@24476
|
351 jnc ReadClusterEven
|
pascal@25454
|
352 %if TINYFAT16 == 0 && FAT16 == 1
|
pascal@25454
|
353 rol ax, cl
|
pascal@25454
|
354 %else
|
pascal@25453
|
355 shr ax, cl
|
pascal@25454
|
356 %endif
|
pascal@24476
|
357 ReadClusterEven:
|
pascal@25094
|
358 scasw ; di += 2
|
pascal@25454
|
359 %if FAT16 == 1
|
pascal@24942
|
360 and ah, dh ; mask cluster value
|
pascal@24942
|
361 cmp ax, dx
|
pascal@25454
|
362 %else
|
pascal@25453
|
363 and ah, 0Fh ; mask cluster value
|
pascal@25453
|
364 cmp ax, 0FF8h
|
pascal@25454
|
365 %endif
|
pascal@25454
|
366 %else
|
pascal@25454
|
367 scasw ; di += 2
|
pascal@25453
|
368 cmp ax, 0FFF8h
|
pascal@25453
|
369 %endif
|
pascal@24476
|
370 xchg ax, si
|
pascal@24476
|
371 jc ClusterLoop
|
pascal@24476
|
372 pop si
|
pascal@24476
|
373 pop di ; file size in sectors
|
pascal@24476
|
374
|
pascal@24476
|
375 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
376 ;; Load the entire file ;;
|
pascal@24476
|
377 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
378 ;; Input: ES:0 -> buffer ;;
|
pascal@24476
|
379 ;; SI = cluster list ;;
|
pascal@24476
|
380 ;; DI = file sectors ;;
|
pascal@24476
|
381 ;; CH = 0 ;;
|
pascal@24945
|
382 ;; BP = 1st data sec ;;
|
pascal@24476
|
383 ;; Output: BP:0 -> buffer ;;
|
pascal@24476
|
384 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
385
|
pascal@24476
|
386 push es
|
pascal@24476
|
387
|
pascal@24476
|
388 ReadClusters:
|
pascal@24476
|
389 lodsw
|
pascal@24476
|
390 dec ax
|
pascal@24476
|
391 dec ax
|
pascal@24476
|
392
|
pascal@25454
|
393 mov cl, [bx(bpbSectorsPerCluster)] ; 1..128
|
pascal@24476
|
394 mul cx ; cx = sector count (ch = 0)
|
pascal@24476
|
395
|
pascal@24476
|
396 add ax, bp ; LBA for cluster data
|
pascal@24476
|
397 adc dx, bx ; dx:ax = LBA
|
pascal@24476
|
398
|
pascal@25454
|
399 call ReadSector ; clear ax, restore dx
|
pascal@24476
|
400
|
pascal@24476
|
401 jne ReadClusters
|
pascal@24476
|
402
|
pascal@24476
|
403 pop bp ; ImageLoadSeg
|
pascal@24476
|
404
|
pascal@24476
|
405 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
406 ;; Type detection, .COM or .EXE? ;;
|
pascal@24476
|
407 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
408
|
pascal@24476
|
409 mov ds, bp ; bp=ds=seg the file is loaded to
|
pascal@24476
|
410
|
pascal@24476
|
411 add bp, [bx+08h] ; bp = image base
|
pascal@24476
|
412 mov di, [bx+18h] ; di = reloc table pointer
|
pascal@24476
|
413
|
pascal@24476
|
414 cmp word [bx], 5A4Dh ; "MZ" signature?
|
pascal@24476
|
415 je RelocateEXE ; yes, it's an EXE program
|
pascal@24476
|
416
|
pascal@24476
|
417 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
418 ;; Setup and run a .COM program ;;
|
pascal@24476
|
419 ;; Set CS=DS=ES=SS SP=0 IP=100h ;;
|
pascal@25454
|
420 ;; AX=0ffffh BX=0 DX=drive and ;;
|
pascal@25454
|
421 ;; cmdline=void ;;
|
pascal@24476
|
422 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
423
|
pascal@24942
|
424 mov di, 100h ; ip
|
pascal@24476
|
425 mov bp, ImageLoadSeg-10h ; "org 100h" stuff :)
|
pascal@24476
|
426 mov ss, bp
|
pascal@24476
|
427 xor sp, sp
|
pascal@24476
|
428 push bp ; cs, ds and es
|
pascal@24476
|
429 jmp short Run
|
pascal@24476
|
430
|
pascal@24476
|
431 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
432 ;; Relocate, setup and run a .EXE program ;;
|
pascal@24476
|
433 ;; Set CS:IP, SS:SP, DS, ES and AX according ;;
|
pascal@24476
|
434 ;; to wiki.osdev.org/MZ#Initial_Program_State ;;
|
pascal@25454
|
435 ;; AX=0ffffh BX=0 DX=drive cmdline=void ;;
|
pascal@24476
|
436 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
437
|
pascal@24476
|
438 ReloCycle:
|
pascal@24476
|
439 add [di+2], bp ; item seg (abs)
|
pascal@24476
|
440 les si, [di] ; si = item ofs, es = item seg
|
pascal@24476
|
441 add [es:si], bp ; fixup
|
pascal@24476
|
442 scasw ; di += 2
|
pascal@24476
|
443 scasw ; point to next entry
|
pascal@24476
|
444
|
pascal@24476
|
445 RelocateEXE:
|
pascal@24942
|
446 dec word [bx+06h] ; reloc items, 32768 max (128KB table)
|
pascal@24942
|
447 jns ReloCycle
|
pascal@24476
|
448 ; PSP don't have a valid drive identifier
|
pascal@24476
|
449 les si, [bx+0Eh]
|
pascal@24476
|
450 add si, bp
|
pascal@24476
|
451 mov ss, si ; ss for EXE
|
pascal@24476
|
452 mov sp, es ; sp for EXE
|
pascal@24476
|
453
|
pascal@24476
|
454 lea si, [bp-10h] ; ds and es both point to the segment
|
pascal@24476
|
455 push si ; containing the PSP structure
|
pascal@24476
|
456
|
pascal@24476
|
457 add bp, [bx+16h] ; cs for EXE
|
pascal@24942
|
458 mov di, [bx+14h] ; ip for EXE
|
pascal@24476
|
459 Run:
|
pascal@24476
|
460 pop ds
|
pascal@24476
|
461 push bp
|
pascal@24942
|
462 push di
|
pascal@24476
|
463 push ds
|
pascal@24476
|
464 pop es
|
pascal@24942
|
465 mov [80h], ax ; clear cmdline
|
pascal@24942
|
466 dec ax ; both FCB in the PSP don't have a valid drive identifier
|
pascal@24476
|
467
|
pascal@24476
|
468 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
469 ;; Set the magic numbers so the program knows that it ;;
|
pascal@24476
|
470 ;; has been loaded by this bootsector and not by MS-DOS ;;
|
pascal@24476
|
471 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
472 mov si, 16381 ; prime number 2**14-3
|
pascal@24476
|
473 mov di, 32749 ; prime number 2**15-19
|
pascal@24476
|
474 mov bp, 65521 ; prime number 2**16-15
|
pascal@24476
|
475
|
pascal@24476
|
476 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
477 ;; All done, transfer control to the program now ;;
|
pascal@24476
|
478 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
479 retf
|
pascal@24476
|
480
|
pascal@24476
|
481 ReadCXSectors:
|
pascal@24476
|
482 mov bp, cx
|
pascal@24476
|
483 add bp, ax ; adjust LBA for cluster data
|
pascal@24476
|
484
|
pascal@24476
|
485 mov di, cx ; no file size limit
|
pascal@24476
|
486
|
pascal@24476
|
487 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
488 ;; Reads sectors using BIOS Int 13h ;;
|
pascal@24476
|
489 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
490 ;; Input: DX:AX = LBA relative to FAT ;;
|
pascal@24476
|
491 ;; BX = 0 ;;
|
pascal@24476
|
492 ;; CX = sector count ;;
|
pascal@24476
|
493 ;; DI = file sectors ;;
|
pascal@24476
|
494 ;; ES:BX -> buffer address ;;
|
pascal@24476
|
495 ;; Output: ES:BX -> next address ;;
|
pascal@24476
|
496 ;; BX = 0 ;;
|
pascal@24476
|
497 ;; CX or DI = 0 ;;
|
pascal@24476
|
498 ;; DL = drive number ;;
|
pascal@24476
|
499 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
500
|
pascal@24476
|
501 ReadSector:
|
pascal@24476
|
502 add ax, [bx(bpbHiddenSectors)]
|
pascal@24476
|
503 adc dx, [bx(bpbHiddenSectors)+2]
|
pascal@24476
|
504 add ax, [bx(bpbReservedSectors)]
|
pascal@24476
|
505
|
pascal@24476
|
506 push si
|
pascal@24476
|
507 ReadSectorNext:
|
pascal@24476
|
508 adc dx, bx
|
pascal@24476
|
509 push di
|
pascal@24476
|
510 push cx
|
pascal@24476
|
511
|
pascal@25450
|
512 %if LBAsupport != 0
|
pascal@24476
|
513 push bx
|
pascal@24476
|
514 push bx
|
pascal@25450
|
515 %endif
|
pascal@24476
|
516 push dx ; 32-bit LBA: up to 2TB
|
pascal@24476
|
517 push ax
|
pascal@24476
|
518 push es
|
pascal@25450
|
519 %if ReadRetry != 0 || LBAsupport != 0
|
pascal@25450
|
520 mov di, 16 ; packet size byte = 16, reserved byte = 0
|
pascal@25450
|
521 %endif
|
pascal@25450
|
522 %if LBAsupport != 0
|
pascal@24476
|
523 push bx
|
pascal@24476
|
524 inc bx ; sector count word = 1
|
pascal@24476
|
525 push bx
|
pascal@24476
|
526 dec bx
|
pascal@24476
|
527 push di
|
pascal@25450
|
528 %endif
|
pascal@24476
|
529
|
pascal@25450
|
530 %if Over2GB != 0
|
pascal@24476
|
531 xchg ax, cx ; save low LBA
|
pascal@24476
|
532 xchg ax, dx ; get high LBA
|
pascal@25452
|
533 cwd ; clear dx (LBA offset <1TB)
|
pascal@25450
|
534 idiv word [bx(bpbSectorsPerTrack)] ; up to 8GB disks
|
pascal@24476
|
535
|
pascal@24476
|
536 xchg ax, cx ; restore low LBA, save high LBA / SPT
|
pascal@25450
|
537 %else
|
pascal@25450
|
538 xor cx, cx ; up to 2GB disks otherwise divide error interrupt !
|
pascal@25450
|
539 %endif
|
pascal@25450
|
540 idiv word [bx(bpbSectorsPerTrack)]
|
pascal@24476
|
541 ; ax = LBA / SPT
|
pascal@24476
|
542 ; dx = LBA % SPT = sector - 1
|
pascal@24476
|
543 inc dx
|
pascal@24476
|
544
|
pascal@24476
|
545 xchg cx, dx ; restore high LBA / SPT, save sector no.
|
pascal@25450
|
546 idiv word [bx(bpbHeadsPerCylinder)]
|
pascal@24476
|
547 ; ax = (LBA / SPT) / HPC = cylinder
|
pascal@24476
|
548 ; dx = (LBA / SPT) % HPC = head
|
pascal@24476
|
549 mov ch, al
|
pascal@24476
|
550 ; ch = LSB 0...7 of cylinder no.
|
pascal@24476
|
551 mov al, 64
|
pascal@24476
|
552 mul ah
|
pascal@24476
|
553 or cl, al
|
pascal@24476
|
554 ; cl = MSB 8...9 of cylinder no. + sector no.
|
pascal@24476
|
555 mov dh, dl
|
pascal@24476
|
556 ; dh = head no.
|
pascal@24476
|
557
|
pascal@24476
|
558 ReadSectorRetry:
|
pascal@25450
|
559 mov dl, [bx(DriveNumber)]
|
pascal@24476
|
560 ; dl = drive no.
|
pascal@25450
|
561 mov si, sp
|
pascal@25450
|
562 %if LBAsupport != 0
|
pascal@24476
|
563 mov ah, 42h ; ah = 42h = extended read function no.
|
pascal@24476
|
564 int 13h ; extended read sectors (DL, DS:SI)
|
pascal@24476
|
565 jnc ReadSectorNextSegment
|
pascal@25450
|
566 %endif
|
pascal@24476
|
567
|
pascal@24476
|
568 mov ax, 201h ; al = sector count = 1
|
pascal@24476
|
569 ; ah = 2 = read function no.
|
pascal@24476
|
570 int 13h ; read sectors (AL, CX, DX, ES:BX)
|
pascal@24476
|
571
|
pascal@24476
|
572 jnc ReadSectorNextSegment
|
pascal@25450
|
573 %if ReadRetry != 0
|
pascal@24476
|
574 cbw ; ah = 0 = reset function
|
pascal@24476
|
575 int 13h ; reset drive (DL)
|
pascal@24476
|
576
|
pascal@24476
|
577 dec di
|
pascal@24476
|
578 jnz ReadSectorRetry ; extra attempt
|
pascal@25450
|
579 %endif
|
pascal@24476
|
580
|
pascal@24476
|
581 call Error
|
pascal@24476
|
582 db "Read error."
|
pascal@24476
|
583
|
pascal@24476
|
584 ReadSectorNextSegment:
|
pascal@24476
|
585
|
pascal@25450
|
586 %if LBAsupport != 0
|
pascal@24476
|
587 pop ax ; al = 16
|
pascal@24476
|
588 mul byte [bx(bpbBytesPerSector)+1] ; = (bpbBytesPerSector/256)*16
|
pascal@24476
|
589 pop cx ; sector count = 1
|
pascal@24476
|
590 pop bx
|
pascal@24476
|
591 add [si+6], ax ; adjust segment for next sector
|
pascal@25450
|
592 %else
|
pascal@25450
|
593 mov al, 16
|
pascal@25450
|
594 mul byte [bx(bpbBytesPerSector)+1] ; = (bpbBytesPerSector/256)*16
|
pascal@25450
|
595 add [si], ax ; adjust segment for next sector
|
pascal@25450
|
596 %endif
|
pascal@24476
|
597 pop es ; es:0 updated
|
pascal@24476
|
598 pop ax
|
pascal@24476
|
599 pop dx
|
pascal@25450
|
600 %if LBAsupport != 0
|
pascal@24476
|
601 pop di
|
pascal@24476
|
602 pop di
|
pascal@24476
|
603 add ax, cx ; adjust LBA for next sector
|
pascal@25450
|
604 %else
|
pascal@25450
|
605 add ax, 1 ; adjust LBA for next sector
|
pascal@25450
|
606 %endif
|
pascal@24476
|
607
|
pascal@24476
|
608 pop cx ; cluster sectors to read
|
pascal@24476
|
609 pop di ; file sectors to read
|
pascal@24476
|
610 dec di ; keep C
|
pascal@24476
|
611 loopne ReadSectorNext ; until cluster sector count or file sector count is reached
|
pascal@24476
|
612 pop si
|
pascal@24942
|
613 mov ax, bx ; clear ax
|
pascal@25450
|
614 mov dx, [bx(DriveNumber)] ; pass the BIOS boot drive to Run or Error
|
pascal@24476
|
615
|
pascal@24476
|
616 ret
|
pascal@24476
|
617
|
pascal@24942
|
618 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24942
|
619 ;; Fill free space with zeroes ;;
|
pascal@24942
|
620 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24942
|
621
|
pascal@24942
|
622 times (512-13-20-($-$$)) db 0
|
pascal@24942
|
623
|
pascal@24476
|
624 ;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
625 ;; Error Messaging Code ;;
|
pascal@24476
|
626 ;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
627
|
pascal@24476
|
628 Error:
|
pascal@24476
|
629 pop si
|
pascal@24478
|
630
|
pascal@24478
|
631 PutStr:
|
pascal@24476
|
632 mov ah, 0Eh
|
pascal@24476
|
633 mov bl, 7
|
pascal@24476
|
634 lodsb
|
pascal@24476
|
635 int 10h
|
pascal@24476
|
636 cmp al, "."
|
pascal@24476
|
637 jne PutStr
|
pascal@24476
|
638
|
pascal@24476
|
639 cbw
|
pascal@24476
|
640 int 16h ; wait for a key...
|
pascal@24476
|
641 int 19h ; bootstrap
|
pascal@24476
|
642
|
pascal@24476
|
643 Stop:
|
pascal@24476
|
644 hlt
|
pascal@24476
|
645 jmp short Stop
|
pascal@24476
|
646
|
pascal@24476
|
647 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
648 ;; Name of the file to load and run ;;
|
pascal@24476
|
649 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
650
|
pascal@24476
|
651 ProgramName db "STARTUP BIN" ; name and extension each must be
|
pascal@25450
|
652 times (510-($-$$)) db ' ' ; padded with spaces (11 bytes total)
|
pascal@25454
|
653 NameLength equ $-ProgramName
|
pascal@24476
|
654
|
pascal@24476
|
655 ;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
656 ;; End of the sector ID ;;
|
pascal@24476
|
657 ;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
658
|
pascal@24476
|
659 ClusterList dw 0AA55h ; BIOS checks for this ID
|
pascal@24479
|
660
|