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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 bootex.asm -f bin -o bootex.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
|
14 ;; - exFAT supported using BIOS int 13h function 42h. ;;
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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 636KB 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 ;; ;;
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pascal@24476
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27 ;; Known Bugs: ;;
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pascal@24476
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28 ;; ~~~~~~~~~~~ ;;
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pascal@24476
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29 ;; - 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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30 ;; on a 128MB qemu image. ;;
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pascal@24476
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31 ;; ;;
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pascal@24476
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32 ;; ;;
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pascal@24476
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33 ;; Memory Layout: ;;
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pascal@24476
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34 ;; ~~~~~~~~~~~~~~ ;;
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pascal@24476
|
35 ;; The diagram below shows the typical memory layout. The actual location ;;
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pascal@24476
|
36 ;; 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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37 ;; reserves memory for its Extended BIOS Data Area just below A0000H and ;;
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pascal@24476
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38 ;; reports less than 640 KB of RAM via its Int 12H function. ;;
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pascal@24476
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39 ;; ;;
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pascal@24476
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40 ;; physical address ;;
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pascal@24476
|
41 ;; +------------------------+ 00000H ;;
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pascal@24476
|
42 ;; | Interrupt Vector Table | ;;
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pascal@24476
|
43 ;; +------------------------+ 00400H ;;
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pascal@24476
|
44 ;; | BIOS Data Area | ;;
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pascal@24476
|
45 ;; +------------------------+ 00500H ;;
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pascal@24476
|
46 ;; | PrtScr Status / Unused | ;;
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pascal@24476
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47 ;; +------------------------+ 00600H ;;
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pascal@24476
|
48 ;; | Loaded Image | ;;
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pascal@24476
|
49 ;; +------------------------+ nnnnnH ;;
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pascal@24476
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50 ;; | Available Memory | ;;
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pascal@24476
|
51 ;; +------------------------+ A0000H - 2KB ;;
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pascal@24476
|
52 ;; | Boot Sector | ;;
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pascal@24476
|
53 ;; +------------------------+ A0000H - 1.5KB ;;
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pascal@24476
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54 ;; | 1.5KB Boot Stack | ;;
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pascal@24476
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55 ;; +------------------------+ A0000H ;;
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pascal@24476
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56 ;; | Video RAM | ;;
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pascal@24476
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57 ;; ;;
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pascal@24476
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58 ;; ;;
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pascal@24476
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59 ;; Boot Image Startup (register values): ;;
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pascal@24476
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60 ;; ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ;;
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pascal@24945
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61 ;; ax = 0ffffh (both FCB in the PSP don't have a valid drive identifier), ;;
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pascal@25454
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62 ;; bx = 0, dl = BIOS boot drive number (e.g. 0, 80H) ;;
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pascal@24476
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63 ;; cs:ip = program entry point ;;
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pascal@24476
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64 ;; ss:sp = program stack (don't confuse with boot sector's stack) ;;
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pascal@24476
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65 ;; COM program defaults: cs = ds = es = ss = 50h, sp = 0, ip = 100h ;;
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pascal@24476
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66 ;; EXE program defaults: ds = es = EXE data - 10h (fake MS-DOS psp), ;;
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pascal@24476
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67 ;; cs:ip and ss:sp depends on EXE header ;;
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pascal@24476
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68 ;; Magic numbers: ;;
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pascal@24476
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69 ;; si = 16381 (prime number 2**14-3) ;;
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pascal@24476
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70 ;; di = 32749 (prime number 2**15-19) ;;
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pascal@24476
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71 ;; bp = 65521 (prime number 2**16-15) ;;
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pascal@24476
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72 ;; The magic numbers let the program know whether it has been loaded by ;;
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pascal@24476
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73 ;; this boot sector or by MS-DOS, which may be handy for universal, bare- ;;
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pascal@24476
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74 ;; metal and MS-DOS programs. ;;
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pascal@24945
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75 ;; The command line contains no arguments. ;;
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pascal@24476
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76 ;; ;;
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pascal@24476
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77 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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78
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pascal@24476
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79 %define bx(label) bx+label-boot
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pascal@25450
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80 %define si(label) si+label-boot
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pascal@25450
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81 NullEntryCheck equ 1 ; +3 bytes
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pascal@25450
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82 ReadRetry equ 1 ; +8 bytes
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pascal@25458
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83 SectorOf512Bytes equ 1 ; -13 bytes
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pascal@24476
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84
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pascal@24476
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85 [BITS 16]
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pascal@24476
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86 [CPU 386]
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pascal@24476
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87
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pascal@24476
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88 ImageLoadSeg equ 60h
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pascal@24476
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89 StackSize equ 1536
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pascal@24476
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90
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pascal@24476
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91 [SECTION .text]
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pascal@24476
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92 [ORG 0]
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pascal@24476
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93
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pascal@24476
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94 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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95 ;; Boot sector starts here ;;
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pascal@24476
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96 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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97
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pascal@24476
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98 boot:
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pascal@25450
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99 DriveNumber:
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pascal@24476
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100 jmp short start ; Windows checks for this jump
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pascal@24476
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101 nop
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pascal@25458
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102 bsOemName times 8 db " " ; 0x03 "EXFAT "
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pascal@24476
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103 times 53 db 0 ; 0x0B
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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 ;; BPB starts here ;;
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pascal@24476
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107 ;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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108
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pascal@24479
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109 bpbSectorStart DQ 0 ; 0x40 partition first sector
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pascal@24479
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110 bpbSectorCount DQ 0 ; 0x48 partition sectors count
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pascal@24479
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111 bpbFatSectorStart DD 0 ; 0x50 FAT first sector
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pascal@24479
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112 bpbFatSectorCount DD 0 ; 0x54 FAT sectors count
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pascal@24479
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113 bpbClusterSectorStart DD 0 ; 0x58 first cluster sector
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pascal@24479
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114 bpbClusterCount DD 0 ; 0x5C total clusters count
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pascal@24479
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115 bpbRootDirCluster DD 0 ; 0x60 first cluster of the root dir
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pascal@24479
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116 bpbVolumeSerial DD 0 ; 0x64 volume serial number
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pascal@24479
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117 bpbFSVersionMinor DB 0 ; 0x68
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pascal@24479
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118 bpbFSVersionMajor DB 0 ; 0x69
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pascal@24479
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119 bpbVolumeStateFlags DW 0 ; 0x6A
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pascal@24479
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120 bpbSectorSizeBits DB 0 ; 0x6C sector size as (1 << n)
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pascal@24479
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121 bpbSectorPerClusterBits DB 0 ; 0x6D sector per cluster as (1 << n)
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pascal@24479
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122 bpbNumberOfFATs DB 0 ; 0x6E always 1
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pascal@24479
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123 bpbDriveNumber DB 0 ; 0x6F alaways 0x80
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pascal@24479
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124 bpbAllocatedPercent DB 0 ; 0x70 percentage of allocated space
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pascal@24476
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125
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pascal@24476
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126 ;;;;;;;;;;;;;;;;;;;
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pascal@24476
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127 ;; BPB ends here ;;
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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 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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131 ;; Boot sector code starts 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@24476
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134 start:
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pascal@24476
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135 cld
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pascal@24476
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136
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pascal@24476
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137 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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138 ;; How much RAM is there? ;;
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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 int 12h ; get conventional memory size (in KBs)
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pascal@24476
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142 mov cx, 106h
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pascal@24476
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143 dec ax
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pascal@24476
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144 dec ax ; reserve 2K bytes for the code and the stack
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pascal@24476
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145 shl ax, cl ; and convert it to 16-byte paragraphs
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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 ;; Reserve memory for the boot sector and its stack ;;
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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 mov es, ax ; cs:0 = ds:0 = ss:0 -> top - 512 - StackSize
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pascal@24476
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152 mov ss, ax
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pascal@24476
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153 mov sp, 512+StackSize ; bytes 0-511 are reserved for the boot code
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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 ;; Copy ourselves to top of memory ;;
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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 mov si, 7C00h
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pascal@24476
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160 xor di, di
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pascal@24476
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161 mov ds, di
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pascal@25450
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162 push es
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pascal@25450
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163 mov [si(DriveNumber)], dx ; store BIOS boot drive number
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pascal@24476
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164 rep movsw ; move 512 bytes (+ 12)
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pascal@24476
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165
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pascal@24476
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166 ;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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167 ;; Jump to the copy ;;
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pascal@24476
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168 ;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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169
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pascal@24942
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170 push word main
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pascal@24476
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171 retf
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pascal@24476
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172
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pascal@24476
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173 main:
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pascal@24476
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174 push cs
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pascal@24476
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175 pop ds
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pascal@24476
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176
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pascal@24476
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177 xor ebx, ebx
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pascal@24476
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178
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pascal@24476
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179 mov esi, [bx(bpbRootDirCluster)] ; esi=cluster # of root dir
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pascal@24476
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180
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pascal@24479
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181 push byte ImageLoadSeg
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pascal@24942
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182 pop es ; cx = 0
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pascal@24476
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183
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pascal@24476
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184 RootDirReadContinue:
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pascal@24476
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185 call ReadCluster ; read one sector of root dir
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pascal@24476
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186
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pascal@24476
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187 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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188 ;; Look for the COM/EXE file to load and run ;;
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pascal@24476
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189 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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190
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pascal@25454
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191 ; es:di -> root entries array
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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 ;; Looks for the file/dir ProgramName ;;
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pascal@24476
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195 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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196 ;; Input: ES:DI -> root directory array ;;
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pascal@24476
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197 ;; Output: ESI = cluster number ;;
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pascal@24476
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198 ;; dword [bx+FileSize] file size ;;
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pascal@24476
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199 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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200
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pascal@25450
|
201 CurNameSize equ 3 ; 1 byte
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pascal@25450
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202 StartCluster equ 14h ; 4 bytes
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pascal@25450
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203 FileSize equ 18h ; 8 bytes
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pascal@24476
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204
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pascal@24476
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205 FindNameCycle:
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pascal@24476
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206 pusha
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pascal@24476
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207
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pascal@25450
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208 %if NullEntryCheck != 0
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pascal@24476
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209 xor ax, ax
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pascal@24476
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210 or al, [es:di]
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pascal@24476
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211 je FindNameFailed
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pascal@25450
|
212 %else
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pascal@25450
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213 movzx ax, byte [es:di]
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pascal@25450
|
214 %endif
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pascal@24476
|
215
|
pascal@24476
|
216 cmp al, 0c0h ; EXFAT_ENTRY_FILE_INFO ?
|
pascal@24476
|
217 jne NotFileInfo
|
pascal@24476
|
218
|
pascal@24942
|
219 mov bl, 31
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pascal@24476
|
220 CopyInfo:
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pascal@24942
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221 mov al, [es:di+bx]
|
pascal@24942
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222 mov [bx], al
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pascal@24476
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223 dec bx
|
pascal@25450
|
224 jnz CopyInfo ; keep BIOS boot drive number
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pascal@24476
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225
|
pascal@24476
|
226 NotFileInfo:
|
pascal@24476
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227 mov al, 0c1h ; EXFAT_ENTRY_FILE_NAME ?
|
pascal@24476
|
228 mov cx, NameLength+1
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pascal@24476
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229 mov si, ProgramName ; ds:si -> program name
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pascal@24476
|
230 CheckName:
|
pascal@24476
|
231 scasw ; compare UTF-16
|
pascal@24476
|
232 lodsb ; with ASCII
|
pascal@24476
|
233 loope CheckName
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pascal@24476
|
234 je FindNameFound ; cx = 0
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pascal@24476
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235 popa ; restore ax, cx, si, di
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pascal@24476
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236
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pascal@24479
|
237 add di, byte 32
|
pascal@24945
|
238 cmp di, bp
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pascal@24945
|
239 jne FindNameCycle ; next root entry
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pascal@25458
|
240 loop RootDirReadContinue ; continue to the next root dir sector
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pascal@25458
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241 cmp esi, byte -10 ; carry=0 if last cluster, and carry=1 otherwise
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pascal@24476
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242 jc RootDirReadContinue ; continue to the next root dir cluster
|
pascal@24476
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243 FindNameFailed: ; end of root directory (dir end reached)
|
pascal@25454
|
244 mov dl, [bx(DriveNumber)] ; restore BIOS boot drive number
|
pascal@24476
|
245 call Error
|
pascal@24476
|
246 db "File not found."
|
pascal@24476
|
247 FindNameFound:
|
pascal@24476
|
248 mov esi, [bx+StartCluster]
|
pascal@24476
|
249
|
pascal@24476
|
250 ;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
|
251 ;; Load the entire file ;;
|
pascal@24476
|
252 ;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
253
|
pascal@24476
|
254 push es
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pascal@25458
|
255 %if SectorOf512Bytes == 0
|
pascal@24945
|
256 xor bp, bp
|
pascal@24476
|
257 FileReadContinue:
|
pascal@24476
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258 shr bp, 4 ; bytes to paragraphs
|
pascal@24476
|
259 mov di, es
|
pascal@24476
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260 add di, bp ; adjust segment for next sector
|
pascal@24476
|
261 mov es, di ; es:0 updated
|
pascal@25458
|
262 %else
|
pascal@25458
|
263 FileReadContinue:
|
pascal@25458
|
264 %endif
|
pascal@24943
|
265 call ReadCluster ; read one more sector of the boot file
|
pascal@25458
|
266 dec cx
|
pascal@25450
|
267 sub [bx+FileSize], ebp ; max FileSize is < 640KB : check low 32 bits only
|
pascal@25458
|
268 %if SectorOf512Bytes != 0
|
pascal@25458
|
269 mov bp, es
|
pascal@25458
|
270 lea bp, [bp+32]
|
pascal@25458
|
271 mov es, bp ; es:0 updated
|
pascal@25458
|
272 %endif
|
pascal@24476
|
273 ja FileReadContinue
|
pascal@25450
|
274 mov dx, [bx(DriveNumber)] ; restore BIOS boot drive number
|
pascal@25454
|
275 xchg ax, di
|
pascal@24476
|
276 pop bp
|
pascal@24476
|
277
|
pascal@24476
|
278 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
279 ;; Type detection, .COM or .EXE? ;;
|
pascal@24476
|
280 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
281
|
pascal@24476
|
282 mov ds, bp ; bp=ds=seg the file is loaded to
|
pascal@24476
|
283
|
pascal@24476
|
284 add bp, [bx+08h] ; bp = image base
|
pascal@24476
|
285 mov di, [bx+18h] ; di = reloc table pointer
|
pascal@24476
|
286
|
pascal@24476
|
287 cmp word [bx], 5A4Dh ; "MZ" signature?
|
pascal@24476
|
288 je RelocateEXE ; yes, it's an EXE program
|
pascal@24476
|
289
|
pascal@24476
|
290 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
291 ;; Setup and run a .COM program ;;
|
pascal@24476
|
292 ;; Set CS=DS=ES=SS SP=0 IP=100h ;;
|
pascal@25454
|
293 ;; AX=0ffffh BX=0 DX=drive and ;;
|
pascal@25454
|
294 ;; cmdline=void ;;
|
pascal@24476
|
295 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
296
|
pascal@24525
|
297 mov di, 100h ; ip
|
pascal@24476
|
298 mov bp, ImageLoadSeg-10h ; "org 100h" stuff :)
|
pascal@24476
|
299 mov ss, bp
|
pascal@24476
|
300 xor sp, sp
|
pascal@24476
|
301 push bp ; cs, ds and es
|
pascal@24476
|
302 jmp short Run
|
pascal@24476
|
303
|
pascal@24476
|
304 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
305 ;; Relocate, setup and run a .EXE program ;;
|
pascal@24476
|
306 ;; Set CS:IP, SS:SP, DS, ES and AX according ;;
|
pascal@24476
|
307 ;; to wiki.osdev.org/MZ#Initial_Program_State ;;
|
pascal@25454
|
308 ;; AX=0ffffh BX=0 DX=drive cmdline=void ;;
|
pascal@24476
|
309 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
310
|
pascal@24476
|
311 ReloCycle:
|
pascal@24476
|
312 add [di+2], bp ; item seg (abs)
|
pascal@24476
|
313 les si, [di] ; si = item ofs, es = item seg
|
pascal@24476
|
314 add [es:si], bp ; fixup
|
pascal@24476
|
315 scasw ; di += 2
|
pascal@24476
|
316 scasw ; point to next entry
|
pascal@24476
|
317
|
pascal@24476
|
318 RelocateEXE:
|
pascal@24942
|
319 dec word [bx+06h] ; reloc items, 32768 max (128KB table)
|
pascal@24942
|
320 jns ReloCycle
|
pascal@24942
|
321
|
pascal@24945
|
322 les si, [bx+0Eh]
|
pascal@24945
|
323 add si, bp
|
pascal@24945
|
324 mov ss, si ; ss for EXE
|
pascal@24945
|
325 mov sp, es ; sp for EXE
|
pascal@24476
|
326
|
pascal@24476
|
327 lea si, [bp-10h] ; ds and es both point to the segment
|
pascal@24476
|
328 push si ; containing the PSP structure
|
pascal@24476
|
329
|
pascal@24476
|
330 add bp, [bx+16h] ; cs for EXE
|
pascal@24525
|
331 mov di, [bx+14h] ; ip for EXE
|
pascal@24476
|
332 Run:
|
pascal@24476
|
333 pop ds
|
pascal@24476
|
334 push bp
|
pascal@24525
|
335 push di
|
pascal@24476
|
336 push ds
|
pascal@24476
|
337 pop es
|
pascal@24942
|
338 mov [80h], ax ; clear cmdline
|
pascal@24942
|
339 dec ax ; both FCB in the PSP don't have a valid drive identifier
|
pascal@24476
|
340
|
pascal@24476
|
341 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
342 ;; Set the magic numbers so the program knows that it ;;
|
pascal@24476
|
343 ;; has been loaded by this bootsector and not by MS-DOS ;;
|
pascal@24476
|
344 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
345 mov si, 16381 ; prime number 2**14-3
|
pascal@24476
|
346 mov di, 32749 ; prime number 2**15-19
|
pascal@24476
|
347 mov bp, 65521 ; prime number 2**16-15
|
pascal@24476
|
348
|
pascal@24476
|
349 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
350 ;; All done, transfer control to the program now ;;
|
pascal@24476
|
351 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
352 retf
|
pascal@24476
|
353
|
pascal@25458
|
354 ;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@25458
|
355 ;; Error Messaging Code ;;
|
pascal@25458
|
356 ;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@25458
|
357
|
pascal@25458
|
358 Error:
|
pascal@25458
|
359 pop si
|
pascal@25458
|
360
|
pascal@25458
|
361 PutStr:
|
pascal@25458
|
362 mov ah, 0Eh
|
pascal@25458
|
363 mov bl, 7
|
pascal@25458
|
364 lodsb
|
pascal@25458
|
365 int 10h
|
pascal@25458
|
366 cmp al, "."
|
pascal@25458
|
367 jne PutStr
|
pascal@25458
|
368
|
pascal@25458
|
369 cbw
|
pascal@25458
|
370 int 16h ; wait for a key...
|
pascal@25458
|
371 int 19h ; bootstrap
|
pascal@25458
|
372
|
pascal@25458
|
373 Stop:
|
pascal@25458
|
374 hlt
|
pascal@25458
|
375 jmp short Stop
|
pascal@25458
|
376
|
pascal@24476
|
377 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
378 ;; Reads a exFAT cluster ;;
|
pascal@24476
|
379 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
380 ;; Input: EDX:EAX = LBA ;;
|
pascal@24476
|
381 ;; EBX = 0 ;;
|
pascal@24476
|
382 ;; CX = sector cnt ;;
|
pascal@24476
|
383 ;; ESI = cluster no ;;
|
pascal@24476
|
384 ;; ES:0 -> buffer adrs ;;
|
pascal@24476
|
385 ;; Output: EBX = 0 ;;
|
pascal@24476
|
386 ;; CX = next cnt ;;
|
pascal@24476
|
387 ;; EBP = bytes/sector;;
|
pascal@24476
|
388 ;; ES:0 -> next adrs ;;
|
pascal@24476
|
389 ;; C=0 for last sector ;;
|
pascal@24476
|
390 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
391
|
pascal@24476
|
392 ReadCluster:
|
pascal@24945
|
393 add eax, byte 1
|
pascal@24945
|
394
|
pascal@24476
|
395 inc cx ; jcxnz
|
pascal@24476
|
396 loop ReadSectorC
|
pascal@24476
|
397
|
pascal@24945
|
398 mul ebx ; edx:eax = 0
|
pascal@25458
|
399 %if SectorOf512Bytes != 0
|
pascal@25458
|
400 mov al, 128
|
pascal@25458
|
401 %else
|
pascal@25452
|
402 mov cl, -2
|
pascal@25450
|
403 add cl, [bx(bpbSectorSizeBits)]
|
pascal@25450
|
404 bts ax, cx ; eax=# of exFAT entries per sector
|
pascal@25458
|
405 %endif
|
pascal@24476
|
406 lea edi, [esi-2] ; edi=cluster #-2
|
pascal@24476
|
407 xchg eax, esi
|
pascal@24476
|
408 div esi ; eax=FAT sector #, edx=entry # in sector
|
pascal@24476
|
409
|
pascal@24525
|
410 imul si, dx, byte 4 ; si=entry # offset in sector
|
pascal@24476
|
411
|
pascal@24476
|
412 cdq
|
pascal@25452
|
413 add eax, [bx(bpbFatSectorStart)] ; sector # relative to exFAT
|
pascal@25454
|
414 call ReadSectorFAT ; read 1 exFAT sector, keep edx=0, set C
|
pascal@24476
|
415
|
pascal@24476
|
416 mov esi, [es:si] ; esi=next cluster #
|
pascal@24476
|
417
|
pascal@25450
|
418 mov dl, [bx(bpbSectorPerClusterBits)]
|
pascal@25452
|
419 xor ecx, ecx
|
pascal@25450
|
420 bts ecx, edx ; 10000h max (32MB cluster)
|
pascal@24476
|
421 xchg eax, edi ; get cluster #-2
|
pascal@24476
|
422 mul ecx
|
pascal@24476
|
423
|
pascal@24476
|
424 add eax, [bx(bpbClusterSectorStart)]
|
pascal@24476
|
425 ReadSectorC:
|
pascal@25454
|
426 mov di, bx
|
pascal@25454
|
427 ReadSectorFAT:
|
pascal@24476
|
428 adc edx, ebx
|
pascal@24476
|
429
|
pascal@24476
|
430 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
431 ;; Reads a sector using BIOS Int 13h ;;
|
pascal@24476
|
432 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
433 ;; Input: EDX:EAX = LBA ;;
|
pascal@24476
|
434 ;; BX = 0 ;;
|
pascal@24476
|
435 ;; CX = sector count ;;
|
pascal@24476
|
436 ;; ES:0 -> buffer address ;;
|
pascal@24476
|
437 ;; Output: BX = 0 ;;
|
pascal@24476
|
438 ;; CX = next count ;;
|
pascal@24476
|
439 ;; EBP = bytes/sector ;;
|
pascal@24476
|
440 ;; ES:0 -> next address ;;
|
pascal@24476
|
441 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
442
|
pascal@25458
|
443 %if SectorOf512Bytes != 0
|
pascal@25458
|
444 lea ebp, [bx+512]
|
pascal@25458
|
445 %else
|
pascal@25458
|
446 lea ebp, [bx+1]
|
pascal@25458
|
447 %endif
|
pascal@24476
|
448
|
pascal@24476
|
449 pushad
|
pascal@24476
|
450
|
pascal@24476
|
451 add eax, [bx(bpbSectorStart)]
|
pascal@24476
|
452 adc edx, [bx(bpbSectorStart)+4]
|
pascal@24476
|
453
|
pascal@24476
|
454 push edx
|
pascal@24476
|
455 push eax
|
pascal@24476
|
456 push es
|
pascal@24476
|
457 push bx
|
pascal@25458
|
458 %if SectorOf512Bytes != 0
|
pascal@25458
|
459 push byte 1 ; sector count word = 1
|
pascal@25458
|
460 %else
|
pascal@24476
|
461 push bp ; sector count word = 1
|
pascal@25458
|
462 %endif
|
pascal@25454
|
463 push byte 16 ; packet size byte = 16, reserved byte = 0
|
pascal@24476
|
464 ReadSectorRetry:
|
pascal@24476
|
465 mov si, sp
|
pascal@24476
|
466 mov ah, 42h ; ah = 42h = extended read function no.
|
pascal@25450
|
467 mov dl, [bx(DriveNumber)] ; restore BIOS boot drive number
|
pascal@24476
|
468 int 13h ; extended read sectors (DL, DS:SI)
|
pascal@24476
|
469
|
pascal@24476
|
470 jnc ReadSuccess
|
pascal@24476
|
471
|
pascal@25450
|
472 %if ReadRetry != 0
|
pascal@24476
|
473 xor ax, ax
|
pascal@24476
|
474 int 13h ; reset drive (DL)
|
pascal@25457
|
475 dec bp
|
pascal@25458
|
476 %if SectorOf512Bytes != 0
|
pascal@25458
|
477 jne ReadSectorRetry ; up to 511 tries
|
pascal@25458
|
478 %else
|
pascal@25457
|
479 jpe ReadSectorRetry ; up to 3 tries
|
pascal@25458
|
480 %endif
|
pascal@25450
|
481 %endif
|
pascal@24476
|
482
|
pascal@24476
|
483 call Error
|
pascal@24476
|
484 db "Read error."
|
pascal@24476
|
485
|
pascal@24476
|
486 ReadSuccess:
|
pascal@25458
|
487 %if SectorOf512Bytes == 0
|
pascal@24476
|
488 mov cl, [bx(bpbSectorSizeBits)]
|
pascal@24476
|
489 shl word [si+16+8], cl ; (e)bp si+16: EDI ESI EBP ESP EBX EDX ECX EAX
|
pascal@25458
|
490 %endif
|
pascal@24476
|
491 popa ; sp += 16
|
pascal@24476
|
492 popad ; real registers
|
pascal@24476
|
493 ret
|
pascal@24476
|
494
|
pascal@24942
|
495 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24942
|
496 ;; Fill free space with zeroes ;;
|
pascal@24942
|
497 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24942
|
498
|
pascal@25458
|
499 times (512-13-($-$$)) db 0
|
pascal@24476
|
500
|
pascal@24476
|
501 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
502 ;; Name of the file to load and run ;;
|
pascal@24476
|
503 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
504
|
pascal@24476
|
505 ProgramName db "startup.bin" ; name and extension
|
pascal@24476
|
506 NameLength equ $-ProgramName
|
pascal@24476
|
507
|
pascal@24476
|
508 ;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
509 ;; End of the sector ID ;;
|
pascal@24476
|
510 ;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
511
|
pascal@24476
|
512 dw 0AA55h ; BIOS checks for this ID
|