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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
|
41 ;; The diagram below shows the typical memory layout. The actual location ;;
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pascal@24476
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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
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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
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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
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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@25458
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87 NullEntryCheck equ 1 ; +2 bytes
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pascal@25450
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88 ReadRetry equ 1 ; +9 bytes
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pascal@25450
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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
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91 GeometryCheck equ 1 ; +18 bytes
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pascal@25458
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92 SectorOf512Bytes equ 1 ; -4/-6 bytes
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pascal@24476
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93
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pascal@24476
|
94 [BITS 16]
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pascal@24476
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95 [CPU 8086]
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pascal@24476
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96
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pascal@24476
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97 ImageLoadSeg equ 60h
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pascal@24476
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98 StackSize equ 3072 ; Stack + cluster list
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pascal@24476
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99
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pascal@24476
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100 [SECTION .text]
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pascal@24476
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101 [ORG 0]
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pascal@24476
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102
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pascal@24476
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103 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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104 ;; Boot sector starts here ;;
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pascal@24476
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105 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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106
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pascal@24476
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107 boot:
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pascal@25450
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108 DriveNumber:
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pascal@24476
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109 jmp short start ; MS-DOS/Windows checks for this jump
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pascal@24476
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110 nop
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pascal@24476
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111 bsOemName DB "BootProg" ; 0x03
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pascal@24476
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112
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pascal@24476
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113 ;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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114 ;; BPB starts here ;;
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pascal@24476
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115 ;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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116
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pascal@24479
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117 bpbBytesPerSector DW 0 ; 0x0B
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pascal@24479
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118 bpbSectorsPerCluster DB 0 ; 0x0D
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pascal@24479
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119 bpbReservedSectors DW 0 ; 0x0E
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pascal@24479
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120 bpbNumberOfFATs DB 0 ; 0x10
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pascal@24479
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121 bpbRootEntries DW 0 ; 0x11
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pascal@24479
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122 bpbTotalSectors DW 0 ; 0x13
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pascal@24479
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123 bpbMedia DB 0 ; 0x15
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pascal@24479
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124 bpbSectorsPerFAT DW 0 ; 0x16
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pascal@24479
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125 bpbSectorsPerTrack DW 0 ; 0x18
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pascal@24479
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126 bpbHeadsPerCylinder DW 0 ; 0x1A
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pascal@24479
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127 bpbHiddenSectors DD 0 ; 0x1C
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pascal@24479
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128 bpbTotalSectorsBig DD 0 ; 0x20
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pascal@24476
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129
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pascal@24476
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130 ;;;;;;;;;;;;;;;;;;;
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pascal@24476
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131 ;; BPB ends here ;;
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pascal@24476
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132 ;;;;;;;;;;;;;;;;;;;
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pascal@24476
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133
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pascal@24479
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134 bsDriveNumber DB 0 ; 0x24
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pascal@24479
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135 bsUnused DB 0 ; 0x25
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pascal@24479
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136 bsExtBootSignature DB 0 ; 0x26
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pascal@24479
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137 bsSerialNumber DD 0 ; 0x27
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pascal@25458
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138 bsVolumeLabel times 11 DB " " ; 0x2B "NO NAME "
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pascal@25458
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139 bsFileSystem times 8 DB " " ; 0x36 "FAT12 " or "FAT16 "
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pascal@24476
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140
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pascal@24476
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141 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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142 ;; Boot sector code starts here ;;
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pascal@24476
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143 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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144
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pascal@24476
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145 start:
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pascal@24476
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146 cld
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pascal@24476
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147
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pascal@24476
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148 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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149 ;; How much RAM is there? ;;
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pascal@24476
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150 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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151
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pascal@24476
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152 int 12h ; get conventional memory size (in KBs)
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pascal@24476
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153 mov cx, 106h
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pascal@24476
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154 shl ax, cl ; and convert it to 16-byte paragraphs
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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 ;; Reserve memory for the boot sector and its stack ;;
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pascal@24476
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158 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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159
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pascal@24476
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160 sub ax, (512+StackSize) /16 ; reserve bytes for the code and the stack
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pascal@24476
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161 mov es, ax ; cs:0 = ds:0 = ss:0 -> top - 512 - StackSize
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pascal@24476
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162 mov ss, ax
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pascal@24476
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163 mov sp, 512+StackSize ; bytes 0-511 are reserved for the boot code
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pascal@24476
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164
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pascal@24476
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165 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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166 ;; Copy ourselves to top of memory ;;
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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 mov si, 7C00h
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pascal@24476
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170 xor di, di
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pascal@24476
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171 mov ds, di
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pascal@25450
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172 push es
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pascal@25450
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173 mov [si(DriveNumber)], dx ; store BIOS boot drive number
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pascal@24476
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174 rep movsw ; move 512 bytes (+ 12)
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pascal@24476
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175
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pascal@24476
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176 ;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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177 ;; Jump to the copy ;;
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pascal@24476
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178 ;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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179
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pascal@24476
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180 mov cl, byte main
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pascal@24476
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181 push cx
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pascal@24476
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182 retf
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pascal@24476
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183
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pascal@24476
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184 main:
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pascal@24476
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185 %if ImageLoadSeg != main-boot
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pascal@24476
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186 %if ImageLoadSeg >= 100h
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pascal@24476
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187 mov cx, ImageLoadSeg
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pascal@24476
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188 %else
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pascal@24476
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189 mov cl, ImageLoadSeg
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pascal@24476
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190 %endif
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pascal@24476
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191 %endif
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pascal@24476
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192 push cx
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pascal@24476
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193
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pascal@24476
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194 ;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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195 ;; Get drive parameters ;;
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pascal@24476
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196 ;; Update heads count ;;
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pascal@24476
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197 ;; for current BIOS ;;
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pascal@24476
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198 ;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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199
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pascal@25450
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200 %if GeometryCheck != 0
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pascal@24476
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201 mov ah, 8
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pascal@24476
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202 int 13h ; may destroy SI,BP, and DS registers
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pascal@25450
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203 %endif
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pascal@24476
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204 ; update AX,BL,CX,DX,DI, and ES registers
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pascal@24476
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205 push cs
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pascal@24476
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206 pop ds
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pascal@24476
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207 xor bx, bx
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pascal@24476
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208
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pascal@25450
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209 %if GeometryCheck != 0
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pascal@24479
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210 and cx, byte 3Fh
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pascal@24476
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211 cmp [bx(bpbSectorsPerTrack)], cx
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pascal@24476
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212 jne BadParams ; verify updated and validity
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pascal@24476
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213 mov al, dh
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pascal@24476
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214 inc ax
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pascal@24476
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215 mov [bpbHeadsPerCylinder], ax
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pascal@24476
|
216 BadParams:
|
pascal@25450
|
217 %endif
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pascal@24476
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218
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pascal@24476
|
219 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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220 ;; Load FAT (FAT12: 6KB max, FAT16: 128KB max) ;;
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pascal@24476
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221 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
|
222
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pascal@24476
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223 pop es ; ImageLoadSeg
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pascal@24476
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224 push es
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pascal@24476
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225
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pascal@24476
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226 mul bx ; dx:ax = 0 = LBA (LBA are relative to FAT)
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pascal@25458
|
227 mov di, word [bx(bpbSectorsPerFAT)]
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pascal@24476
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228
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pascal@25458
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229 call ReadDISectors ; read fat; clear ax, cx, di; bp = SectorsPerFAT
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pascal@24476
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230
|
pascal@24476
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231 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
|
232 ;; load the root directory in ;;
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pascal@24476
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233 ;; its entirety (16KB max) ;;
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pascal@24476
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234 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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235
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pascal@25458
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236 %if SectorOf512Bytes != 0
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pascal@25458
|
237 mov di, word [bx(bpbRootEntries)]
|
pascal@25458
|
238 mov cl, 4
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pascal@25458
|
239 shr di, cl ; di = root directory size in sectors
|
pascal@25458
|
240 %else
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pascal@24942
|
241 mov al, 32
|
pascal@24476
|
242
|
pascal@24476
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243 mul word [bx(bpbRootEntries)]
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pascal@24476
|
244 div word [bx(bpbBytesPerSector)]
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pascal@25458
|
245 xchg ax, di ; di = root directory size in sectors, clear ah
|
pascal@25458
|
246 %endif
|
pascal@24476
|
247
|
pascal@24476
|
248 mov al, [bpbNumberOfFATs]
|
pascal@25458
|
249 mul bp ; [bx(bpbSectorsPerFAT)], set by ReadDISectors
|
pascal@24476
|
250
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pascal@25457
|
251 push es ; read root directory
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pascal@25458
|
252 call ReadDISectors ; clear ax, cx, di; bp = first data sector
|
pascal@24476
|
253 pop es
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pascal@24476
|
254
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pascal@24476
|
255 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
|
256 ;; Look for the COM/EXE file to load and run ;;
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pascal@24476
|
257 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
|
258
|
pascal@24476
|
259 ; es:di -> root entries array
|
pascal@24476
|
260
|
pascal@24476
|
261 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
|
262 ;; Looks for the file/dir ProgramName ;;
|
pascal@24476
|
263 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
264 ;; Input: ES:DI -> root directory array ;;
|
pascal@24476
|
265 ;; Output: SI = cluster number ;;
|
pascal@24476
|
266 ;; AX = file sector count ;;
|
pascal@24476
|
267 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
268
|
pascal@24476
|
269 FindNameCycle:
|
pascal@24476
|
270 push di
|
pascal@25454
|
271 mov cl, NameLength
|
pascal@24476
|
272 mov si, ProgramName ; ds:si -> program name
|
pascal@24476
|
273 repe cmpsb
|
pascal@24476
|
274 pop di
|
pascal@24476
|
275 je FindNameFound
|
pascal@25450
|
276 %if NullEntryCheck != 0
|
pascal@25458
|
277 scasb ; Z == NC
|
pascal@25458
|
278 cmc
|
pascal@25458
|
279 lea di, [di+31]
|
pascal@25458
|
280 dec word [bx(bpbRootEntries)]
|
pascal@25458
|
281 ja FindNameCycle ; next root entry
|
pascal@25450
|
282 %else
|
pascal@25450
|
283 add di, byte 32
|
pascal@24476
|
284 dec word [bx(bpbRootEntries)]
|
pascal@24476
|
285 jnz FindNameCycle ; next root entry
|
pascal@25458
|
286 %endif
|
pascal@24476
|
287
|
pascal@24476
|
288 FindNameFailed:
|
pascal@24476
|
289 call Error
|
pascal@24476
|
290 db "File not found."
|
pascal@24476
|
291
|
pascal@24476
|
292 FindNameFound:
|
pascal@24476
|
293 push si
|
pascal@24476
|
294 mov si, [es:di+1Ah] ; si = cluster no.
|
pascal@24476
|
295 les ax, [es:di+1Ch] ; file size
|
pascal@24476
|
296 mov dx, es
|
pascal@24476
|
297 div word [bx(bpbBytesPerSector)]
|
pascal@24476
|
298 cmp bx, dx ; sector aligned ?
|
pascal@24476
|
299 adc ax, bx ; file last sector
|
pascal@24476
|
300 pop di ; di = ClusterList
|
pascal@24476
|
301
|
pascal@24476
|
302 pop es ; ImageLoadSeg
|
pascal@24476
|
303 push ax
|
pascal@24476
|
304
|
pascal@24476
|
305 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
306 ;; build cluster list ;;
|
pascal@24476
|
307 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
308 ;; Input: ES:0 -> FAT ;;
|
pascal@24476
|
309 ;; SI = first cluster ;;
|
pascal@24476
|
310 ;; DI = cluster list :;
|
pascal@24476
|
311 ;; CH = 0 ;;
|
pascal@24476
|
312 ;; Output: SI = cluster list ;;
|
pascal@24476
|
313 ;; CH = 0 ;;
|
pascal@24476
|
314 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
315
|
pascal@25458
|
316 FAT12 equ 1
|
pascal@25458
|
317 FAT16 equ 1
|
pascal@25458
|
318 TINYFAT16 equ 1
|
pascal@25453
|
319 push di ; up to 2 * 635K / BytesPerCluster = 2540 bytes
|
pascal@25450
|
320 %if FAT12 == 1
|
pascal@25454
|
321 mov cl, 12
|
pascal@25450
|
322 %endif
|
pascal@24476
|
323 ClusterLoop:
|
pascal@24476
|
324 mov [di], si
|
pascal@25450
|
325 add si, si ; si = cluster * 2
|
pascal@25450
|
326 %if FAT16 == 1
|
pascal@24476
|
327 mov ax, es ; ax = FAT segment = ImageLoadSeg
|
pascal@25094
|
328 jnc First64k
|
pascal@24476
|
329 mov ah, (1000h+ImageLoadSeg)>>8 ; adjust segment for 2nd part of FAT16
|
pascal@25094
|
330 First64k:
|
pascal@25453
|
331 %if FAT12 == 1
|
pascal@25457
|
332 mov dx, 0FFF6h
|
pascal@25454
|
333 %if TINYFAT16 == 1
|
pascal@25453
|
334 test [bx(bsFileSystem+4)], cl ; FAT12 or FAT16 ? clear C
|
pascal@25458
|
335 jne ReadClusterFat16
|
pascal@25454
|
336 %else
|
pascal@25454
|
337 cmp [bx(bpbSectorsPerFAT)], cx ; 1..12 = FAT12, 16..256 = FAT16
|
pascal@25458
|
338 ja ReadClusterFat16
|
pascal@25454
|
339 %endif
|
pascal@24942
|
340 mov dh, 0Fh
|
pascal@25453
|
341 %endif
|
pascal@25450
|
342 %endif
|
pascal@25450
|
343 %if FAT12 == 1
|
pascal@25087
|
344 add si, [di]
|
pascal@24476
|
345 shr si, 1 ; si = cluster * 3 / 2
|
pascal@25450
|
346 %endif
|
pascal@25450
|
347 %if FAT16 == 1
|
pascal@24942
|
348 ReadClusterFat16:
|
pascal@25094
|
349 push ds
|
pascal@25087
|
350 mov ds, ax
|
pascal@24476
|
351 lodsw ; ax = next cluster
|
pascal@25094
|
352 pop ds
|
pascal@25450
|
353 %else
|
pascal@25453
|
354 es lodsw
|
pascal@25450
|
355 %endif
|
pascal@25450
|
356 %if FAT12 == 1
|
pascal@24476
|
357 jnc ReadClusterEven
|
pascal@25454
|
358 rol ax, cl
|
pascal@24476
|
359 ReadClusterEven:
|
pascal@25094
|
360 scasw ; di += 2
|
pascal@25454
|
361 %if FAT16 == 1
|
pascal@24942
|
362 and ah, dh ; mask cluster value
|
pascal@24942
|
363 cmp ax, dx
|
pascal@25454
|
364 %else
|
pascal@25453
|
365 and ah, 0Fh ; mask cluster value
|
pascal@25457
|
366 cmp ax, 0FF6h
|
pascal@25454
|
367 %endif
|
pascal@25454
|
368 %else
|
pascal@25454
|
369 scasw ; di += 2
|
pascal@25457
|
370 cmp ax, 0FFF6h
|
pascal@25453
|
371 %endif
|
pascal@24476
|
372 xchg ax, si
|
pascal@24476
|
373 jc ClusterLoop
|
pascal@24476
|
374 pop si
|
pascal@24476
|
375 pop di ; file size in sectors
|
pascal@24476
|
376
|
pascal@24476
|
377 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
378 ;; Load the entire file ;;
|
pascal@24476
|
379 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
380 ;; Input: ES:0 -> buffer ;;
|
pascal@24476
|
381 ;; SI = cluster list ;;
|
pascal@24476
|
382 ;; DI = file sectors ;;
|
pascal@24476
|
383 ;; CH = 0 ;;
|
pascal@24945
|
384 ;; BP = 1st data sec ;;
|
pascal@24476
|
385 ;; Output: BP:0 -> buffer ;;
|
pascal@24476
|
386 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
387
|
pascal@24476
|
388 push es
|
pascal@24476
|
389
|
pascal@24476
|
390 ReadClusters:
|
pascal@24476
|
391 lodsw
|
pascal@24476
|
392 dec ax
|
pascal@24476
|
393 dec ax
|
pascal@24476
|
394
|
pascal@25454
|
395 mov cl, [bx(bpbSectorsPerCluster)] ; 1..128
|
pascal@24476
|
396 mul cx ; cx = sector count (ch = 0)
|
pascal@24476
|
397
|
pascal@24476
|
398 add ax, bp ; LBA for cluster data
|
pascal@24476
|
399 adc dx, bx ; dx:ax = LBA
|
pascal@24476
|
400
|
pascal@25458
|
401 call ReadSectors ; clear ax, restore dx
|
pascal@24476
|
402
|
pascal@25458
|
403 jne ReadClusters ; until end of file
|
pascal@24476
|
404
|
pascal@24476
|
405 pop bp ; ImageLoadSeg
|
pascal@24476
|
406
|
pascal@24476
|
407 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
408 ;; Type detection, .COM or .EXE? ;;
|
pascal@24476
|
409 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
410
|
pascal@24476
|
411 mov ds, bp ; bp=ds=seg the file is loaded to
|
pascal@24476
|
412
|
pascal@24476
|
413 add bp, [bx+08h] ; bp = image base
|
pascal@24476
|
414 mov di, [bx+18h] ; di = reloc table pointer
|
pascal@24476
|
415
|
pascal@24476
|
416 cmp word [bx], 5A4Dh ; "MZ" signature?
|
pascal@24476
|
417 je RelocateEXE ; yes, it's an EXE program
|
pascal@24476
|
418
|
pascal@24476
|
419 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
420 ;; Setup and run a .COM program ;;
|
pascal@24476
|
421 ;; Set CS=DS=ES=SS SP=0 IP=100h ;;
|
pascal@25454
|
422 ;; AX=0ffffh BX=0 DX=drive and ;;
|
pascal@25454
|
423 ;; cmdline=void ;;
|
pascal@24476
|
424 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
425
|
pascal@24942
|
426 mov di, 100h ; ip
|
pascal@24476
|
427 mov bp, ImageLoadSeg-10h ; "org 100h" stuff :)
|
pascal@24476
|
428 mov ss, bp
|
pascal@24476
|
429 xor sp, sp
|
pascal@24476
|
430 push bp ; cs, ds and es
|
pascal@24476
|
431 jmp short Run
|
pascal@24476
|
432
|
pascal@24476
|
433 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
434 ;; Relocate, setup and run a .EXE program ;;
|
pascal@24476
|
435 ;; Set CS:IP, SS:SP, DS, ES and AX according ;;
|
pascal@24476
|
436 ;; to wiki.osdev.org/MZ#Initial_Program_State ;;
|
pascal@25454
|
437 ;; AX=0ffffh BX=0 DX=drive cmdline=void ;;
|
pascal@24476
|
438 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
439
|
pascal@24476
|
440 ReloCycle:
|
pascal@24476
|
441 add [di+2], bp ; item seg (abs)
|
pascal@24476
|
442 les si, [di] ; si = item ofs, es = item seg
|
pascal@24476
|
443 add [es:si], bp ; fixup
|
pascal@24476
|
444 scasw ; di += 2
|
pascal@24476
|
445 scasw ; point to next entry
|
pascal@24476
|
446
|
pascal@24476
|
447 RelocateEXE:
|
pascal@24942
|
448 dec word [bx+06h] ; reloc items, 32768 max (128KB table)
|
pascal@24942
|
449 jns ReloCycle
|
pascal@24476
|
450 ; PSP don't have a valid drive identifier
|
pascal@24476
|
451 les si, [bx+0Eh]
|
pascal@24476
|
452 add si, bp
|
pascal@24476
|
453 mov ss, si ; ss for EXE
|
pascal@24476
|
454 mov sp, es ; sp for EXE
|
pascal@24476
|
455
|
pascal@24476
|
456 lea si, [bp-10h] ; ds and es both point to the segment
|
pascal@24476
|
457 push si ; containing the PSP structure
|
pascal@24476
|
458
|
pascal@24476
|
459 add bp, [bx+16h] ; cs for EXE
|
pascal@24942
|
460 mov di, [bx+14h] ; ip for EXE
|
pascal@24476
|
461 Run:
|
pascal@24476
|
462 pop ds
|
pascal@24476
|
463 push bp
|
pascal@24942
|
464 push di
|
pascal@24476
|
465 push ds
|
pascal@24476
|
466 pop es
|
pascal@24942
|
467 mov [80h], ax ; clear cmdline
|
pascal@24942
|
468 dec ax ; both FCB in the PSP don't have a valid drive identifier
|
pascal@24476
|
469
|
pascal@24476
|
470 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
471 ;; Set the magic numbers so the program knows that it ;;
|
pascal@24476
|
472 ;; has been loaded by this bootsector and not by MS-DOS ;;
|
pascal@24476
|
473 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
474 mov si, 16381 ; prime number 2**14-3
|
pascal@24476
|
475 mov di, 32749 ; prime number 2**15-19
|
pascal@24476
|
476 mov bp, 65521 ; prime number 2**16-15
|
pascal@24476
|
477
|
pascal@24476
|
478 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
479 ;; All done, transfer control to the program now ;;
|
pascal@24476
|
480 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
481 retf
|
pascal@24476
|
482
|
pascal@25458
|
483 ;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@25458
|
484 ;; Error Messaging Code ;;
|
pascal@25458
|
485 ;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@25458
|
486
|
pascal@25458
|
487 Error:
|
pascal@25458
|
488 pop si
|
pascal@25458
|
489
|
pascal@25458
|
490 PutStr:
|
pascal@25458
|
491 mov ah, 0Eh
|
pascal@25458
|
492 mov bl, 7
|
pascal@25458
|
493 lodsb
|
pascal@25458
|
494 int 10h
|
pascal@25458
|
495 cmp al, "."
|
pascal@25458
|
496 jne PutStr
|
pascal@25458
|
497
|
pascal@25458
|
498 cbw
|
pascal@25458
|
499 int 16h ; wait for a key...
|
pascal@25458
|
500 int 19h ; bootstrap
|
pascal@25458
|
501
|
pascal@25458
|
502 Stop:
|
pascal@25458
|
503 hlt
|
pascal@25458
|
504 jmp short Stop
|
pascal@25458
|
505
|
pascal@25458
|
506 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@25458
|
507 ;; Read sectors using BIOS Int 13h ;;
|
pascal@25458
|
508 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@25458
|
509 ;; Input: DX:AX = LBA relative to FAT ;;
|
pascal@25458
|
510 ;; BX = 0 ;;
|
pascal@25458
|
511 ;; DI = sector count ;;
|
pascal@25458
|
512 ;; ES:BX -> buffer address ;;
|
pascal@25458
|
513 ;; Output: ES:BX -> next address ;;
|
pascal@25458
|
514 ;; BX = 0 ;;
|
pascal@25458
|
515 ;; CX = 0 ;;
|
pascal@25458
|
516 ;; DI = 0 ;;
|
pascal@25458
|
517 ;; DL = drive number ;;
|
pascal@25458
|
518 ;; DX:BP = next LBA from FAT ;;
|
pascal@25458
|
519 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@25458
|
520
|
pascal@25458
|
521 ReadDISectors:
|
pascal@25458
|
522 mov bp, di
|
pascal@24476
|
523 add bp, ax ; adjust LBA for cluster data
|
pascal@24476
|
524
|
pascal@25458
|
525 mov cx, di ; no cluster size limit
|
pascal@24476
|
526
|
pascal@24476
|
527 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@25458
|
528 ;; Read sectors using BIOS Int 13h ;;
|
pascal@24476
|
529 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
530 ;; Input: DX:AX = LBA relative to FAT ;;
|
pascal@24476
|
531 ;; BX = 0 ;;
|
pascal@24476
|
532 ;; CX = sector count ;;
|
pascal@24476
|
533 ;; DI = file sectors ;;
|
pascal@24476
|
534 ;; ES:BX -> buffer address ;;
|
pascal@24476
|
535 ;; Output: ES:BX -> next address ;;
|
pascal@24476
|
536 ;; BX = 0 ;;
|
pascal@24476
|
537 ;; CX or DI = 0 ;;
|
pascal@24476
|
538 ;; DL = drive number ;;
|
pascal@24476
|
539 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
540
|
pascal@25458
|
541 ReadSectors:
|
pascal@24476
|
542 add ax, [bx(bpbHiddenSectors)]
|
pascal@24476
|
543 adc dx, [bx(bpbHiddenSectors)+2]
|
pascal@24476
|
544 add ax, [bx(bpbReservedSectors)]
|
pascal@24476
|
545
|
pascal@24476
|
546 push si
|
pascal@24476
|
547 ReadSectorNext:
|
pascal@24476
|
548 adc dx, bx
|
pascal@24476
|
549 push di
|
pascal@24476
|
550 push cx
|
pascal@24476
|
551
|
pascal@25450
|
552 %if LBAsupport != 0
|
pascal@24476
|
553 push bx
|
pascal@24476
|
554 push bx
|
pascal@25450
|
555 %endif
|
pascal@24476
|
556 push dx ; 32-bit LBA: up to 2TB
|
pascal@24476
|
557 push ax
|
pascal@24476
|
558 push es
|
pascal@25450
|
559 %if ReadRetry != 0 || LBAsupport != 0
|
pascal@25450
|
560 mov di, 16 ; packet size byte = 16, reserved byte = 0
|
pascal@25450
|
561 %endif
|
pascal@25450
|
562 %if LBAsupport != 0
|
pascal@24476
|
563 push bx
|
pascal@24476
|
564 inc bx ; sector count word = 1
|
pascal@24476
|
565 push bx
|
pascal@24476
|
566 dec bx
|
pascal@24476
|
567 push di
|
pascal@25450
|
568 %endif
|
pascal@24476
|
569
|
pascal@25450
|
570 %if Over2GB != 0
|
pascal@24476
|
571 xchg ax, cx ; save low LBA
|
pascal@24476
|
572 xchg ax, dx ; get high LBA
|
pascal@25452
|
573 cwd ; clear dx (LBA offset <1TB)
|
pascal@25450
|
574 idiv word [bx(bpbSectorsPerTrack)] ; up to 8GB disks
|
pascal@24476
|
575
|
pascal@24476
|
576 xchg ax, cx ; restore low LBA, save high LBA / SPT
|
pascal@25450
|
577 %else
|
pascal@25450
|
578 xor cx, cx ; up to 2GB disks otherwise divide error interrupt !
|
pascal@25450
|
579 %endif
|
pascal@25450
|
580 idiv word [bx(bpbSectorsPerTrack)]
|
pascal@24476
|
581 ; ax = LBA / SPT
|
pascal@24476
|
582 ; dx = LBA % SPT = sector - 1
|
pascal@24476
|
583 inc dx
|
pascal@24476
|
584
|
pascal@24476
|
585 xchg cx, dx ; restore high LBA / SPT, save sector no.
|
pascal@25450
|
586 idiv word [bx(bpbHeadsPerCylinder)]
|
pascal@24476
|
587 ; ax = (LBA / SPT) / HPC = cylinder
|
pascal@24476
|
588 ; dx = (LBA / SPT) % HPC = head
|
pascal@25458
|
589
|
pascal@25458
|
590 xchg ch, al ; clear al
|
pascal@24476
|
591 ; ch = LSB 0...7 of cylinder no.
|
pascal@25458
|
592 shr ax, 1
|
pascal@25458
|
593 shr ax, 1
|
pascal@24476
|
594 or cl, al
|
pascal@24476
|
595 ; cl = MSB 8...9 of cylinder no. + sector no.
|
pascal@24476
|
596 mov dh, dl
|
pascal@24476
|
597 ; dh = head no.
|
pascal@24476
|
598
|
pascal@24476
|
599 ReadSectorRetry:
|
pascal@25450
|
600 mov dl, [bx(DriveNumber)]
|
pascal@24476
|
601 ; dl = drive no.
|
pascal@25450
|
602 mov si, sp
|
pascal@25450
|
603 %if LBAsupport != 0
|
pascal@24476
|
604 mov ah, 42h ; ah = 42h = extended read function no.
|
pascal@24476
|
605 int 13h ; extended read sectors (DL, DS:SI)
|
pascal@24476
|
606 jnc ReadSectorNextSegment
|
pascal@25450
|
607 %endif
|
pascal@24476
|
608
|
pascal@24476
|
609 mov ax, 201h ; al = sector count = 1
|
pascal@24476
|
610 ; ah = 2 = read function no.
|
pascal@24476
|
611 int 13h ; read sectors (AL, CX, DX, ES:BX)
|
pascal@24476
|
612
|
pascal@24476
|
613 jnc ReadSectorNextSegment
|
pascal@25450
|
614 %if ReadRetry != 0
|
pascal@24476
|
615 cbw ; ah = 0 = reset function
|
pascal@24476
|
616 int 13h ; reset drive (DL)
|
pascal@24476
|
617
|
pascal@24476
|
618 dec di
|
pascal@25457
|
619 jnz ReadSectorRetry ; up to 15 extra attempt
|
pascal@25450
|
620 %endif
|
pascal@24476
|
621
|
pascal@24476
|
622 call Error
|
pascal@24476
|
623 db "Read error."
|
pascal@24476
|
624
|
pascal@24476
|
625 ReadSectorNextSegment:
|
pascal@24476
|
626
|
pascal@25450
|
627 %if LBAsupport != 0
|
pascal@24476
|
628 pop ax ; al = 16
|
pascal@25458
|
629 %if SectorOf512Bytes != 0
|
pascal@25458
|
630 add word [si+6], byte 32 ; adjust segment for next sector
|
pascal@25458
|
631 %else
|
pascal@24476
|
632 mul byte [bx(bpbBytesPerSector)+1] ; = (bpbBytesPerSector/256)*16
|
pascal@25458
|
633 add [si+6], ax ; adjust segment for next sector
|
pascal@25458
|
634 %endif
|
pascal@24476
|
635 pop cx ; sector count = 1
|
pascal@24476
|
636 pop bx
|
pascal@25450
|
637 %else
|
pascal@25458
|
638 %if SectorOf512Bytes != 0
|
pascal@25458
|
639 add word [si], byte 32 ; adjust segment for next sector
|
pascal@25458
|
640 %else
|
pascal@25450
|
641 mov al, 16
|
pascal@25450
|
642 mul byte [bx(bpbBytesPerSector)+1] ; = (bpbBytesPerSector/256)*16
|
pascal@25450
|
643 add [si], ax ; adjust segment for next sector
|
pascal@25458
|
644 %endif
|
pascal@25450
|
645 %endif
|
pascal@24476
|
646 pop es ; es:0 updated
|
pascal@24476
|
647 pop ax
|
pascal@24476
|
648 pop dx
|
pascal@25450
|
649 %if LBAsupport != 0
|
pascal@24476
|
650 pop di
|
pascal@24476
|
651 pop di
|
pascal@24476
|
652 add ax, cx ; adjust LBA for next sector
|
pascal@25450
|
653 %else
|
pascal@25450
|
654 add ax, 1 ; adjust LBA for next sector
|
pascal@25450
|
655 %endif
|
pascal@24476
|
656
|
pascal@24476
|
657 pop cx ; cluster sectors to read
|
pascal@24476
|
658 pop di ; file sectors to read
|
pascal@24476
|
659 dec di ; keep C
|
pascal@25457
|
660 loopne ReadSectorNext ; until cluster sector count or file sector count
|
pascal@24476
|
661 pop si
|
pascal@24942
|
662 mov ax, bx ; clear ax
|
pascal@25450
|
663 mov dx, [bx(DriveNumber)] ; pass the BIOS boot drive to Run or Error
|
pascal@24476
|
664
|
pascal@24476
|
665 ret
|
pascal@24476
|
666
|
pascal@24942
|
667 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24942
|
668 ;; Fill free space with zeroes ;;
|
pascal@24942
|
669 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24942
|
670
|
pascal@25458
|
671 times (512-13-($-$$)) db 0
|
pascal@24476
|
672
|
pascal@24476
|
673 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
674 ;; Name of the file to load and run ;;
|
pascal@24476
|
675 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
676
|
pascal@24476
|
677 ProgramName db "STARTUP BIN" ; name and extension each must be
|
pascal@25450
|
678 times (510-($-$$)) db ' ' ; padded with spaces (11 bytes total)
|
pascal@25454
|
679 NameLength equ $-ProgramName
|
pascal@24476
|
680
|
pascal@24476
|
681 ;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
682 ;; End of the sector ID ;;
|
pascal@24476
|
683 ;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
684
|
pascal@24476
|
685 ClusterList dw 0AA55h ; BIOS checks for this ID
|