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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
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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@25460
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19 ;; Its maximum size can be up to 637KB 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
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41 ;; +------------------------+ 00000H ;;
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pascal@24476
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42 ;; | Interrupt Vector Table | ;;
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pascal@24476
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43 ;; +------------------------+ 00400H ;;
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pascal@24476
|
44 ;; | BIOS Data Area | ;;
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pascal@24476
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45 ;; +------------------------+ 00500H ;;
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pascal@24476
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46 ;; | PrtScr Status / Unused | ;;
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pascal@24476
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47 ;; +------------------------+ 00600H ;;
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pascal@24476
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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@25460
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51 ;; +------------------------+ A0000H - 1KB ;;
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pascal@24476
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52 ;; | Boot Sector | ;;
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pascal@25460
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53 ;; +------------------------+ A0000H - 0.5KB ;;
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pascal@25460
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54 ;; | 0.5KB 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@25569
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81 NullEntryCheck equ 1 ; +3/5 bytes
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pascal@25569
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82 ReadRetry equ 1 ; +7 bytes
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pascal@25569
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83 SectorOf512Bytes equ 0 ; -12 bytes
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pascal@25569
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84 CheckAttrib equ 0 ; +16/18 bytes
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pascal@25564
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85 WaitForKey equ 0 ; +5 bytes
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pascal@25564
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86 TfatSupport equ 1 ; +10 bytes
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pascal@25564
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87 CheckLBAsupport equ 0 ; +11/21 bytes
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pascal@24476
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88
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pascal@24476
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89 [BITS 16]
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pascal@24476
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90 [CPU 386]
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pascal@24476
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91
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pascal@24476
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92 ImageLoadSeg equ 60h
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pascal@25460
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93 StackSize equ 512
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pascal@24476
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94
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pascal@24476
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95 [SECTION .text]
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pascal@24476
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96 [ORG 0]
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pascal@24476
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97
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pascal@24476
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98 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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99 ;; Boot sector starts here ;;
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pascal@24476
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100 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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101
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pascal@24476
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102 boot:
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pascal@25450
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103 DriveNumber:
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pascal@24476
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104 jmp short start ; Windows checks for this jump
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pascal@24476
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105 nop
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pascal@25458
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106 bsOemName times 8 db " " ; 0x03 "EXFAT "
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pascal@24476
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107 times 53 db 0 ; 0x0B
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pascal@24476
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108
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pascal@24476
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109 ;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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110 ;; BPB starts here ;;
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pascal@24476
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111 ;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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112
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pascal@24479
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113 bpbSectorStart DQ 0 ; 0x40 partition first sector
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pascal@24479
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114 bpbSectorCount DQ 0 ; 0x48 partition sectors count
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pascal@24479
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115 bpbFatSectorStart DD 0 ; 0x50 FAT first sector
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pascal@24479
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116 bpbFatSectorCount DD 0 ; 0x54 FAT sectors count
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pascal@24479
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117 bpbClusterSectorStart DD 0 ; 0x58 first cluster sector
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pascal@24479
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118 bpbClusterCount DD 0 ; 0x5C total clusters count
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pascal@24479
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119 bpbRootDirCluster DD 0 ; 0x60 first cluster of the root dir
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pascal@24479
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120 bpbVolumeSerial DD 0 ; 0x64 volume serial number
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pascal@24479
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121 bpbFSVersionMinor DB 0 ; 0x68
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pascal@24479
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122 bpbFSVersionMajor DB 0 ; 0x69
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pascal@25564
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123 bpbVolumeStateFlags DW 0 ; 0x6A bit0 = fat used, bit1 = dirty, bit2 = media error
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pascal@24479
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124 bpbSectorSizeBits DB 0 ; 0x6C sector size as (1 << n)
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pascal@24479
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125 bpbSectorPerClusterBits DB 0 ; 0x6D sector per cluster as (1 << n)
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pascal@25564
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126 bpbNumberOfFATs DB 0 ; 0x6E always 1 or 2 (Tfat case)
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pascal@25564
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127 bpbDriveNumber DB 0 ; 0x6F always 0x80
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pascal@24479
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128 bpbAllocatedPercent DB 0 ; 0x70 percentage of allocated space
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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@24476
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134 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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135 ;; Boot sector code starts here ;;
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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 start:
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pascal@24476
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139 cld
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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 ;; How much RAM is there? ;;
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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 int 12h ; get conventional memory size (in KBs)
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pascal@24476
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146 mov cx, 106h
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pascal@25460
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147 dec ax ; reserve 1K bytes for the code and the stack
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pascal@24476
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148 shl ax, cl ; and convert it to 16-byte paragraphs
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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 ;; Reserve memory for the boot sector and its stack ;;
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pascal@24476
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152 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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153
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pascal@24476
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154 mov es, ax ; cs:0 = ds:0 = ss:0 -> top - 512 - StackSize
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pascal@24476
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155 mov ss, ax
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pascal@24476
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156 mov sp, 512+StackSize ; bytes 0-511 are reserved for the boot code
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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 ;; Copy ourselves to top of memory ;;
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pascal@24476
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160 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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161
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pascal@24476
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162 mov si, 7C00h
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pascal@24476
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163 xor di, di
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pascal@24476
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164 mov ds, di
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pascal@25450
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165 push es
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pascal@25450
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166 mov [si(DriveNumber)], dx ; store BIOS boot drive number
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pascal@24476
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167 rep movsw ; move 512 bytes (+ 12)
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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@24476
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170 ;; Jump to the copy ;;
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pascal@24476
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171 ;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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172
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pascal@24942
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173 push word main
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pascal@24476
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174 retf
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pascal@24476
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175
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pascal@25564
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176 %if CheckLBAsupport != 0
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pascal@25564
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177 %macro BootFileName 0
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pascal@24476
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178 main:
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pascal@25564
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179 mov ah, 41h ; clobbers AX, BX, CX, DH
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pascal@25564
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180 mov bx, 55AAh
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pascal@25564
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181 int 13h
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pascal@25564
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182 jc ReadError
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pascal@25564
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183 ; xor bx, 0AA55h
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pascal@25564
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184 ; jnz ReadError
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pascal@25564
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185 ; shr cx, 1 ; function 42h support ?
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pascal@25564
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186 ; jnc ReadError
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pascal@25564
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187 xor cx, cx
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pascal@25564
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188 %else
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pascal@25564
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189 main:
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pascal@25564
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190 %endif
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pascal@24476
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191 push cs
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pascal@24476
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192 pop ds
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pascal@24476
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193
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pascal@24476
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194 xor ebx, ebx
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pascal@24476
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195
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pascal@24476
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196 mov esi, [bx(bpbRootDirCluster)] ; esi=cluster # of root dir
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pascal@24476
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197
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pascal@24479
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198 push byte ImageLoadSeg
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pascal@24942
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199 pop es ; cx = 0
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pascal@24476
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200
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pascal@24476
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201 RootDirReadContinue:
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pascal@24476
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202 call ReadCluster ; read one sector of root dir
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pascal@24476
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203
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pascal@24476
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204 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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205 ;; Look for the COM/EXE file to load and run ;;
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pascal@24476
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206 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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207
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pascal@25454
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208 ; es:di -> root entries array
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pascal@24476
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209
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pascal@24476
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210 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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211 ;; Looks for the file/dir ProgramName ;;
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pascal@24476
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212 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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213 ;; Input: ES:DI -> root directory array ;;
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pascal@24476
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214 ;; Output: ESI = cluster number ;;
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pascal@24476
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215 ;; dword [bx+FileSize] file size ;;
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pascal@24476
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216 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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217
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pascal@25467
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218 CurNameSize equ 03h ; 1 byte
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pascal@25450
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219 StartCluster equ 14h ; 4 bytes
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pascal@25450
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220 FileSize equ 18h ; 8 bytes
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pascal@24476
|
221
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pascal@24476
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222 FindNameCycle:
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pascal@24476
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223 pusha
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pascal@24476
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224
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pascal@25564
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225 %if NullEntryCheck != 0
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pascal@25564
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226 xor ax, ax
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pascal@25564
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227 or al, [es:di]
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pascal@25564
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228 je FindNameFailed
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pascal@25564
|
229 %define curtag al
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pascal@25564
|
230 %define chktag al
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pascal@25564
|
231 %else
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pascal@25564
|
232 %define curtag byte [es:di]
|
pascal@25564
|
233 %define chktag ax
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pascal@25564
|
234 %endif
|
pascal@25564
|
235 cmp curtag, 0c0h ; EXFAT_ENTRY_FILE_INFO ?
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pascal@25564
|
236 jne NotFileInfo
|
pascal@25564
|
237
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pascal@25564
|
238 mov bl, 32
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pascal@25564
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239 CopyInfo:
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pascal@25564
|
240 mov [bx], al
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pascal@25564
|
241 dec bx
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pascal@25564
|
242 mov al, [es:di+bx]
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pascal@25564
|
243 jnz CopyInfo ; keep BIOS boot drive number
|
pascal@25564
|
244
|
pascal@25564
|
245 NotFileInfo:
|
pascal@25469
|
246 %if CheckAttrib != 0
|
pascal@25469
|
247 Attributes equ 0Bh ; 1 byte
|
pascal@25564
|
248 cmp curtag, 85h ; EXFAT_ENTRY_FILE ?
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pascal@25469
|
249 jne NotEntryFile
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pascal@25469
|
250 mov al, [es:di+Attributes]
|
pascal@25550
|
251 mov [ProgramName+NameLength+1], al
|
pascal@25469
|
252 NotEntryFile:
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pascal@25469
|
253 %endif
|
pascal@25564
|
254 mov chktag, 0c1h ; EXFAT_ENTRY_FILE_NAME ?
|
pascal@24476
|
255 mov cx, NameLength+1
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pascal@24476
|
256 mov si, ProgramName ; ds:si -> program name
|
pascal@24476
|
257 CheckName:
|
pascal@24476
|
258 scasw ; compare UTF-16
|
pascal@24476
|
259 lodsb ; with ASCII
|
pascal@24476
|
260 loope CheckName
|
pascal@25467
|
261 VolumeLabel equ 8
|
pascal@25467
|
262 SubDirectory equ 10h
|
pascal@25564
|
263 %if CheckAttrib != 0
|
pascal@25467
|
264 jnz SkipFindName
|
pascal@25550
|
265 test byte [si], VolumeLabel+SubDirectory
|
pascal@25467
|
266 SkipFindName:
|
pascal@25467
|
267 %endif
|
pascal@24476
|
268 je FindNameFound ; cx = 0
|
pascal@24476
|
269 popa ; restore ax, cx, si, di
|
pascal@24476
|
270
|
pascal@24479
|
271 add di, byte 32
|
pascal@24945
|
272 cmp di, bp
|
pascal@24945
|
273 jne FindNameCycle ; next root entry
|
pascal@25458
|
274 loop RootDirReadContinue ; continue to the next root dir sector
|
pascal@25458
|
275 cmp esi, byte -10 ; carry=0 if last cluster, and carry=1 otherwise
|
pascal@24476
|
276 jc RootDirReadContinue ; continue to the next root dir cluster
|
pascal@24476
|
277 FindNameFailed: ; end of root directory (dir end reached)
|
pascal@25454
|
278 mov dl, [bx(DriveNumber)] ; restore BIOS boot drive number
|
pascal@24476
|
279 call Error
|
pascal@24476
|
280 db "File not found."
|
pascal@24476
|
281 FindNameFound:
|
pascal@24476
|
282 mov esi, [bx+StartCluster]
|
pascal@24476
|
283
|
pascal@24476
|
284 ;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
285 ;; Load the entire file ;;
|
pascal@25550
|
286 ;; Input: ESI = cluster ;;
|
pascal@25550
|
287 ;; CX = 0 ;;
|
pascal@24476
|
288 ;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
289
|
pascal@24476
|
290 push es
|
pascal@25458
|
291 %if SectorOf512Bytes == 0
|
pascal@24945
|
292 xor bp, bp
|
pascal@24476
|
293 FileReadContinue:
|
pascal@24476
|
294 shr bp, 4 ; bytes to paragraphs
|
pascal@24476
|
295 mov di, es
|
pascal@24476
|
296 add di, bp ; adjust segment for next sector
|
pascal@24476
|
297 mov es, di ; es:0 updated
|
pascal@25458
|
298 %else
|
pascal@25458
|
299 FileReadContinue:
|
pascal@25458
|
300 %endif
|
pascal@24943
|
301 call ReadCluster ; read one more sector of the boot file
|
pascal@25458
|
302 dec cx
|
pascal@25450
|
303 sub [bx+FileSize], ebp ; max FileSize is < 640KB : check low 32 bits only
|
pascal@25458
|
304 %if SectorOf512Bytes != 0
|
pascal@25458
|
305 mov bp, es
|
pascal@25458
|
306 lea bp, [bp+32]
|
pascal@25458
|
307 mov es, bp ; es:0 updated
|
pascal@25458
|
308 %endif
|
pascal@24476
|
309 ja FileReadContinue
|
pascal@25450
|
310 mov dx, [bx(DriveNumber)] ; restore BIOS boot drive number
|
pascal@25454
|
311 xchg ax, di
|
pascal@24476
|
312 pop bp
|
pascal@24476
|
313
|
pascal@24476
|
314 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
315 ;; Type detection, .COM or .EXE? ;;
|
pascal@24476
|
316 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
317
|
pascal@24476
|
318 mov ds, bp ; bp=ds=seg the file is loaded to
|
pascal@24476
|
319
|
pascal@24476
|
320 add bp, [bx+08h] ; bp = image base
|
pascal@24476
|
321 mov di, [bx+18h] ; di = reloc table pointer
|
pascal@24476
|
322
|
pascal@24476
|
323 cmp word [bx], 5A4Dh ; "MZ" signature?
|
pascal@24476
|
324 je RelocateEXE ; yes, it's an EXE program
|
pascal@24476
|
325
|
pascal@24476
|
326 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
327 ;; Setup and run a .COM program ;;
|
pascal@24476
|
328 ;; Set CS=DS=ES=SS SP=0 IP=100h ;;
|
pascal@25454
|
329 ;; AX=0ffffh BX=0 DX=drive and ;;
|
pascal@25454
|
330 ;; cmdline=void ;;
|
pascal@24476
|
331 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
332
|
pascal@24525
|
333 mov di, 100h ; ip
|
pascal@24476
|
334 mov bp, ImageLoadSeg-10h ; "org 100h" stuff :)
|
pascal@24476
|
335 mov ss, bp
|
pascal@24476
|
336 xor sp, sp
|
pascal@24476
|
337 push bp ; cs, ds and es
|
pascal@24476
|
338 jmp short Run
|
pascal@24476
|
339
|
pascal@24476
|
340 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
341 ;; Relocate, setup and run a .EXE program ;;
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pascal@24476
|
342 ;; Set CS:IP, SS:SP, DS, ES and AX according ;;
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pascal@24476
|
343 ;; to wiki.osdev.org/MZ#Initial_Program_State ;;
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pascal@25454
|
344 ;; AX=0ffffh BX=0 DX=drive cmdline=void ;;
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pascal@24476
|
345 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
|
346
|
pascal@24476
|
347 ReloCycle:
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pascal@24476
|
348 add [di+2], bp ; item seg (abs)
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pascal@24476
|
349 les si, [di] ; si = item ofs, es = item seg
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pascal@24476
|
350 add [es:si], bp ; fixup
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pascal@24476
|
351 scasw ; di += 2
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pascal@24476
|
352 scasw ; point to next entry
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pascal@24476
|
353
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pascal@24476
|
354 RelocateEXE:
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pascal@24942
|
355 dec word [bx+06h] ; reloc items, 32768 max (128KB table)
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pascal@24942
|
356 jns ReloCycle
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pascal@24942
|
357
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pascal@24945
|
358 les si, [bx+0Eh]
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pascal@24945
|
359 add si, bp
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pascal@24945
|
360 mov ss, si ; ss for EXE
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pascal@24945
|
361 mov sp, es ; sp for EXE
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pascal@24476
|
362
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pascal@24476
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363 lea si, [bp-10h] ; ds and es both point to the segment
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pascal@24476
|
364 push si ; containing the PSP structure
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pascal@24476
|
365
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pascal@24476
|
366 add bp, [bx+16h] ; cs for EXE
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pascal@24525
|
367 mov di, [bx+14h] ; ip for EXE
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pascal@24476
|
368 Run:
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pascal@24476
|
369 pop ds
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pascal@24476
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370 push bp
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pascal@24525
|
371 push di
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pascal@24476
|
372 push ds
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pascal@24476
|
373 pop es
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pascal@24942
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374 mov [80h], ax ; clear cmdline
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pascal@24942
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375 dec ax ; both FCB in the PSP don't have a valid drive identifier
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pascal@24476
|
376
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pascal@24476
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377 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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378 ;; Set the magic numbers so the program knows that it ;;
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pascal@24476
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379 ;; has been loaded by this bootsector and not by MS-DOS ;;
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pascal@24476
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380 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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381 mov si, 16381 ; prime number 2**14-3
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pascal@24476
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382 mov di, 32749 ; prime number 2**15-19
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pascal@24476
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383 mov bp, 65521 ; prime number 2**16-15
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pascal@24476
|
384
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pascal@24476
|
385 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
|
386 ;; All done, transfer control to the program now ;;
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pascal@24476
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387 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
|
388 retf
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pascal@25564
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389 %if CheckLBAsupport != 0
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pascal@25564
|
390 %endm
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pascal@25564
|
391 %endif
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pascal@24476
|
392
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pascal@25458
|
393 ;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@25458
|
394 ;; Error Messaging Code ;;
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pascal@25458
|
395 ;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@25458
|
396
|
pascal@25458
|
397 Error:
|
pascal@25458
|
398 pop si
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pascal@25458
|
399
|
pascal@25458
|
400 PutStr:
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pascal@25458
|
401 mov ah, 0Eh
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pascal@25458
|
402 mov bl, 7
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pascal@25458
|
403 lodsb
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pascal@25458
|
404 int 10h
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pascal@25458
|
405 cmp al, "."
|
pascal@25458
|
406 jne PutStr
|
pascal@25564
|
407 %if WaitForKey != 0
|
pascal@25458
|
408 cbw
|
pascal@25458
|
409 int 16h ; wait for a key...
|
pascal@25458
|
410 int 19h ; bootstrap
|
pascal@25564
|
411 %endif
|
pascal@25458
|
412 Stop:
|
pascal@25458
|
413 hlt
|
pascal@25458
|
414 jmp short Stop
|
pascal@25458
|
415
|
pascal@24476
|
416 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
|
417 ;; Reads a exFAT cluster ;;
|
pascal@24476
|
418 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
|
419 ;; Input: EDX:EAX = LBA ;;
|
pascal@25564
|
420 ;; EBX = 0 ;;
|
pascal@24476
|
421 ;; CX = sector cnt ;;
|
pascal@24476
|
422 ;; ESI = cluster no ;;
|
pascal@24476
|
423 ;; ES:0 -> buffer adrs ;;
|
pascal@25550
|
424 ;; Output: EDX:EAX = next LBA ;;
|
pascal@25550
|
425 ;; CX = sector cnt ;;
|
pascal@25550
|
426 ;; ESI = cluster no ;;
|
pascal@24476
|
427 ;; EBP = bytes/sector;;
|
pascal@25550
|
428 ;; Keep: EDI = 0 ;;
|
pascal@24476
|
429 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
430
|
pascal@24476
|
431 ReadCluster:
|
pascal@24945
|
432 add eax, byte 1
|
pascal@24945
|
433
|
pascal@24476
|
434 inc cx ; jcxnz
|
pascal@24476
|
435 loop ReadSectorC
|
pascal@24476
|
436
|
pascal@24945
|
437 mul ebx ; edx:eax = 0
|
pascal@25458
|
438 %if SectorOf512Bytes != 0
|
pascal@25458
|
439 mov al, 128
|
pascal@25564
|
440 %define SectorPerClusterBits [bx(bpbSectorPerClusterBits)]
|
pascal@25458
|
441 %else
|
pascal@25550
|
442 mov ah, 40h
|
pascal@25550
|
443 mov cx, [bx(bpbSectorSizeBits)]
|
pascal@25564
|
444 %define SectorPerClusterBits ch
|
pascal@25550
|
445 rol ax, cl ; eax=# of exFAT entries per sector
|
pascal@25458
|
446 %endif
|
pascal@24476
|
447 lea edi, [esi-2] ; edi=cluster #-2
|
pascal@24476
|
448 xchg eax, esi
|
pascal@24476
|
449 div esi ; eax=FAT sector #, edx=entry # in sector
|
pascal@24476
|
450
|
pascal@24525
|
451 imul si, dx, byte 4 ; si=entry # offset in sector
|
pascal@24476
|
452
|
pascal@24476
|
453 cdq
|
pascal@25452
|
454 add eax, [bx(bpbFatSectorStart)] ; sector # relative to exFAT
|
pascal@25564
|
455 %if TfatSupport
|
pascal@25564
|
456 test byte [bx(bpbVolumeStateFlags)], 1
|
pascal@25564
|
457 jz UseFat0
|
pascal@25564
|
458 add eax, [bx(bpbFatSectorCount)]
|
pascal@25564
|
459 UseFat0:
|
pascal@25564
|
460 %endif
|
pascal@25454
|
461 call ReadSectorFAT ; read 1 exFAT sector, keep edx=0, set C
|
pascal@24476
|
462
|
pascal@24476
|
463 mov esi, [es:si] ; esi=next cluster #
|
pascal@24476
|
464
|
pascal@25564
|
465 mov dl, SectorPerClusterBits
|
pascal@25452
|
466 xor ecx, ecx
|
pascal@25450
|
467 bts ecx, edx ; 10000h max (32MB cluster)
|
pascal@24476
|
468 xchg eax, edi ; get cluster #-2
|
pascal@24476
|
469 mul ecx
|
pascal@24476
|
470
|
pascal@24476
|
471 add eax, [bx(bpbClusterSectorStart)]
|
pascal@24476
|
472 ReadSectorC:
|
pascal@25454
|
473 mov di, bx
|
pascal@25454
|
474 ReadSectorFAT:
|
pascal@24476
|
475 adc edx, ebx
|
pascal@24476
|
476
|
pascal@24476
|
477 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
478 ;; Reads a sector using BIOS Int 13h ;;
|
pascal@24476
|
479 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
480 ;; Input: EDX:EAX = LBA ;;
|
pascal@25564
|
481 ;; EBX = 0 ;;
|
pascal@24476
|
482 ;; ES:0 -> buffer address ;;
|
pascal@25550
|
483 ;; Output: EBP = bytes/sector ;;
|
pascal@25550
|
484 ;; Keep: ESI = cluster ;;
|
pascal@25550
|
485 ;; EDI = FAT sector or 0 ;;
|
pascal@25550
|
486 ;; ECX = sector count ;;
|
pascal@24476
|
487 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
488
|
pascal@25458
|
489 %if SectorOf512Bytes != 0
|
pascal@25458
|
490 lea ebp, [bx+512]
|
pascal@25458
|
491 %else
|
pascal@25458
|
492 lea ebp, [bx+1]
|
pascal@25458
|
493 %endif
|
pascal@24476
|
494
|
pascal@24476
|
495 pushad
|
pascal@24476
|
496
|
pascal@24476
|
497 add eax, [bx(bpbSectorStart)]
|
pascal@24476
|
498 adc edx, [bx(bpbSectorStart)+4]
|
pascal@24476
|
499
|
pascal@24476
|
500 push edx
|
pascal@24476
|
501 push eax
|
pascal@24476
|
502 push es
|
pascal@24476
|
503 push bx
|
pascal@25458
|
504 %if SectorOf512Bytes != 0
|
pascal@25458
|
505 push byte 1 ; sector count word = 1
|
pascal@25458
|
506 %else
|
pascal@24476
|
507 push bp ; sector count word = 1
|
pascal@25458
|
508 %endif
|
pascal@25454
|
509 push byte 16 ; packet size byte = 16, reserved byte = 0
|
pascal@24476
|
510 ReadSectorRetry:
|
pascal@24476
|
511 mov si, sp
|
pascal@24476
|
512 mov ah, 42h ; ah = 42h = extended read function no.
|
pascal@25450
|
513 mov dl, [bx(DriveNumber)] ; restore BIOS boot drive number
|
pascal@24476
|
514 int 13h ; extended read sectors (DL, DS:SI)
|
pascal@24476
|
515
|
pascal@24476
|
516 jnc ReadSuccess
|
pascal@24476
|
517
|
pascal@25450
|
518 %if ReadRetry != 0
|
pascal@24476
|
519 xor ax, ax
|
pascal@24476
|
520 int 13h ; reset drive (DL)
|
pascal@25457
|
521 dec bp
|
pascal@25458
|
522 %if SectorOf512Bytes != 0
|
pascal@25458
|
523 jne ReadSectorRetry ; up to 511 tries
|
pascal@25458
|
524 %else
|
pascal@25457
|
525 jpe ReadSectorRetry ; up to 3 tries
|
pascal@25458
|
526 %endif
|
pascal@25450
|
527 %endif
|
pascal@24476
|
528
|
pascal@25564
|
529 ReadError:
|
pascal@24476
|
530 call Error
|
pascal@24476
|
531 db "Read error."
|
pascal@24476
|
532
|
pascal@24476
|
533 ReadSuccess:
|
pascal@25458
|
534 %if SectorOf512Bytes == 0
|
pascal@24476
|
535 mov cl, [bx(bpbSectorSizeBits)]
|
pascal@24476
|
536 shl word [si+16+8], cl ; (e)bp si+16: EDI ESI EBP ESP EBX EDX ECX EAX
|
pascal@25458
|
537 %endif
|
pascal@24476
|
538 popa ; sp += 16
|
pascal@24476
|
539 popad ; real registers
|
pascal@24476
|
540 ret
|
pascal@24476
|
541
|
pascal@25564
|
542 %if CheckLBAsupport != 0
|
pascal@25564
|
543 BootFileName
|
pascal@25564
|
544 %endif
|
pascal@25564
|
545
|
pascal@24942
|
546 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24942
|
547 ;; Fill free space with zeroes ;;
|
pascal@24942
|
548 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24942
|
549
|
pascal@25458
|
550 times (512-13-($-$$)) db 0
|
pascal@24476
|
551
|
pascal@24476
|
552 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
553 ;; Name of the file to load and run ;;
|
pascal@24476
|
554 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
555
|
pascal@25463
|
556 NameLength equ 11
|
pascal@25463
|
557 ProgramName times NameLength db 0 ; name and extension
|
pascal@24476
|
558
|
pascal@24476
|
559 ;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
560 ;; End of the sector ID ;;
|
pascal@24476
|
561 ;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
562
|
pascal@24476
|
563 dw 0AA55h ; BIOS checks for this ID
|