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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 boot32.asm -f bin -o boot32.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@24535
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14 ;; - FAT32 supported using BIOS int 13h function 42h (IOW, it will only ;;
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pascal@24535
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15 ;; work with modern BIOSes supporting HDDs bigger than 8 GB) ;;
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pascal@24476
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16 ;; ;;
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pascal@24476
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17 ;; - Loads a 16-bit executable file in the MS-DOS .COM or .EXE format ;;
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pascal@24476
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18 ;; from the root directory of a disk and transfers control to it ;;
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pascal@24476
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19 ;; (the "ProgramName" variable holds the name of the file to be loaded) ;;
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pascal@25460
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20 ;; Its maximum size can be up to 637KB without Extended BIOS Data area. ;;
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pascal@24476
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21 ;; ;;
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pascal@24476
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22 ;; - Prints an error if the file isn't found or couldn't be read ;;
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pascal@24476
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23 ;; ("File not found" or "Read error") ;;
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pascal@24476
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24 ;; and waits for a key to be pressed, then executes the Int 19h ;;
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pascal@24476
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25 ;; instruction and lets the BIOS continue bootstrap. ;;
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pascal@24476
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26 ;; ;;
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pascal@24476
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27 ;; ;;
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pascal@24476
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28 ;; Known Bugs: ;;
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pascal@24476
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29 ;; ~~~~~~~~~~~ ;;
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pascal@24476
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30 ;; - 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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31 ;; on my HDD and an 8GB USB stick. ;;
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pascal@24476
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32 ;; ;;
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pascal@24476
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33 ;; ;;
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pascal@24476
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34 ;; Memory Layout: ;;
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pascal@24476
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35 ;; ~~~~~~~~~~~~~~ ;;
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pascal@24476
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36 ;; The diagram below shows the typical memory layout. The actual location ;;
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pascal@24476
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37 ;; 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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38 ;; reserves memory for its Extended BIOS Data Area just below A0000H and ;;
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pascal@24476
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39 ;; reports less than 640 KB of RAM via its Int 12H function. ;;
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pascal@24476
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40 ;; ;;
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pascal@24476
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41 ;; physical address ;;
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pascal@24476
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42 ;; +------------------------+ 00000H ;;
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pascal@24476
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43 ;; | Interrupt Vector Table | ;;
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pascal@24476
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44 ;; +------------------------+ 00400H ;;
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pascal@24476
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45 ;; | BIOS Data Area | ;;
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pascal@24476
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46 ;; +------------------------+ 00500H ;;
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pascal@24476
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47 ;; | PrtScr Status / Unused | ;;
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pascal@24476
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48 ;; +------------------------+ 00600H ;;
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pascal@24476
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49 ;; | Loaded Image | ;;
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pascal@24476
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50 ;; +------------------------+ nnnnnH ;;
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pascal@24476
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51 ;; | Available Memory | ;;
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pascal@25460
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52 ;; +------------------------+ A0000H - 1KB ;;
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pascal@24476
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53 ;; | Boot Sector | ;;
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pascal@25460
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54 ;; +------------------------+ A0000H - 0.5KB ;;
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pascal@25460
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55 ;; | 0.5KB Boot Stack | ;;
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pascal@24476
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56 ;; +------------------------+ A0000H ;;
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pascal@24476
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57 ;; | Video RAM | ;;
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pascal@24476
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58 ;; ;;
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pascal@24476
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59 ;; ;;
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pascal@24476
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60 ;; Boot Image Startup (register values): ;;
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pascal@24476
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61 ;; ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ;;
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pascal@24945
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62 ;; ax = 0ffffh (both FCB in the PSP don't have a valid drive identifier), ;;
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pascal@25454
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63 ;; bx = 0, dl = BIOS boot drive number (e.g. 0, 80H) ;;
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pascal@24476
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64 ;; cs:ip = program entry point ;;
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pascal@24476
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65 ;; ss:sp = program stack (don't confuse with boot sector's stack) ;;
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pascal@24476
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66 ;; COM program defaults: cs = ds = es = ss = 50h, sp = 0, ip = 100h ;;
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pascal@24476
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67 ;; EXE program defaults: ds = es = EXE data - 10h (fake MS-DOS psp), ;;
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pascal@24476
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68 ;; cs:ip and ss:sp depends on EXE header ;;
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pascal@24476
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69 ;; Magic numbers: ;;
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pascal@24476
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70 ;; si = 16381 (prime number 2**14-3) ;;
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pascal@24476
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71 ;; di = 32749 (prime number 2**15-19) ;;
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pascal@24476
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72 ;; bp = 65521 (prime number 2**16-15) ;;
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pascal@24476
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73 ;; The magic numbers let the program know whether it has been loaded by ;;
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pascal@24476
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74 ;; this boot sector or by MS-DOS, which may be handy for universal, bare- ;;
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pascal@24476
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75 ;; metal and MS-DOS programs. ;;
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pascal@24945
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76 ;; The command line contains no arguments. ;;
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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
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pascal@24491
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80 %define bx(label) bx+label-boot
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pascal@25449
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81 %define si(label) si+label-boot
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pascal@25485
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82 ExtraBootSector equ 1
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pascal@25449
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83 ClusterMask equ 1 ; +9 bytes
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pascal@25460
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84 NullEntryCheck equ 1 ; +5 bytes
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pascal@25485
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85 CheckAttrib equ 1 ; +6 bytes
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pascal@25485
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86 NonMirroredFATs equ 1 ; +18 bytes
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pascal@25449
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87 ReadRetry equ 1 ; +7 bytes
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pascal@25458
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88 LBA48bits equ 1 ; +15 bytes
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pascal@25485
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89 CHSsupport equ 1 ; +27 bytes max 16MB, 32MB or 8GB
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pascal@25485
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90 CHSupTo32MB equ 1 ; +6 bytes
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pascal@25485
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91 CHSupTo8GB equ 1 ; +14 bytes
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pascal@25485
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92 SectorOf512Bytes equ 0 ; -5 bytes
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pascal@25458
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93 Always2FATs equ 0 ; -4 bytes
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pascal@24491
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94
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pascal@24476
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95 [BITS 16]
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pascal@24476
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96
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pascal@24478
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97 ImageLoadSeg equ 60h ; <=07Fh because of "push byte ImageLoadSeg" instructions
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pascal@25460
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98 StackSize equ 512
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pascal@24476
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99
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pascal@24476
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100 [SECTION .text]
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pascal@24476
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101 [ORG 0]
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pascal@24476
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102
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pascal@24476
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103 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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104 ;; Boot sector starts here ;;
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pascal@24476
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105 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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106
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pascal@24491
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107 boot:
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pascal@25458
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108 DriveNumber equ boot+0
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pascal@25458
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109 HiLBA equ boot+2
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pascal@24476
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110 jmp short start ; MS-DOS/Windows checks for this jump
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pascal@24476
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111 nop
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pascal@24476
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112 bsOemName DB "BootProg" ; 0x03
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pascal@24476
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113
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pascal@24476
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114 ;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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115 ;; BPB1 starts here ;;
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pascal@24476
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116 ;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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117
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pascal@24479
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118 bpbBytesPerSector DW 0 ; 0x0B
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pascal@24479
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119 bpbSectorsPerCluster DB 0 ; 0x0D
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pascal@24479
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120 bpbReservedSectors DW 0 ; 0x0E
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pascal@24479
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121 bpbNumberOfFATs DB 0 ; 0x10
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pascal@24479
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122 bpbRootEntries DW 0 ; 0x11
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pascal@24479
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123 bpbTotalSectors DW 0 ; 0x13
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pascal@24479
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124 bpbMedia DB 0 ; 0x15
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pascal@24479
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125 bpbSectorsPerFAT DW 0 ; 0x16
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pascal@24479
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126 bpbSectorsPerTrack DW 0 ; 0x18
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pascal@24479
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127 bpbHeadsPerCylinder DW 0 ; 0x1A
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pascal@24479
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128 bpbHiddenSectors DD 0 ; 0x1C
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pascal@24479
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129 bpbTotalSectorsBig DD 0 ; 0x20
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pascal@24476
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130
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pascal@24476
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131 ;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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132 ;; BPB1 ends here ;;
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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 ;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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136 ;; BPB2 starts here ;;
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pascal@24476
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137 ;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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138
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pascal@24479
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139 bsSectorsPerFAT32 DD 0 ; 0x24
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pascal@24479
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140 bsExtendedFlags DW 0 ; 0x28
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pascal@24479
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141 bsFSVersion DW 0 ; 0x2A
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pascal@24479
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142 bsRootDirectoryClusterNo DD 0 ; 0x2C
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pascal@24479
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143 bsFSInfoSectorNo DW 0 ; 0x30
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pascal@24479
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144 bsBackupBootSectorNo DW 0 ; 0x32
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pascal@24479
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145 bsreserved times 12 DB 0 ; 0x34
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pascal@24479
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146 bsDriveNumber DB 0 ; 0x40
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pascal@24479
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147 bsreserved1 DB 0 ; 0x41
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pascal@24479
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148 bsExtendedBootSignature DB 0 ; 0x42
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pascal@24479
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149 bsVolumeSerialNumber DD 0 ; 0x43
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pascal@25458
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150 bsVolumeLabel times 11 DB " " ; 0x47 "NO NAME "
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pascal@25458
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151 bsFileSystemName times 8 DB " " ; 0x52 "FAT32 "
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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 ;; BPB2 ends here ;;
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pascal@24476
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155 ;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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156
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pascal@24476
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157 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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158 ;; Boot sector code starts here ;;
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pascal@24476
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159 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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160
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pascal@24476
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161 start:
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pascal@24476
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162 cld
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pascal@24476
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163
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pascal@24476
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164 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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165 ;; How much RAM is there? ;;
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pascal@24476
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166 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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167
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pascal@24476
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168 int 12h ; get conventional memory size (in KBs)
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pascal@25460
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169 dec ax ; reserve 1K bytes for the code and the stack
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pascal@24525
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170 mov cx, 106h
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pascal@24525
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171 shl ax, cl ; and convert it to 16-byte paragraphs
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pascal@24476
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172
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pascal@24476
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173 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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174 ;; Reserve memory for the boot sector and its stack ;;
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pascal@24476
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175 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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176
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pascal@24525
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177 mov es, ax ; cs:0 = ds:0 = ss:0 -> top - 512 - StackSize
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pascal@25485
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178 %if ExtraBootSector == 0
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pascal@24525
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179 mov ss, ax
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pascal@24525
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180 mov sp, 512+StackSize ; bytes 0-511 are reserved for the boot code
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pascal@25485
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181 %endif
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pascal@24476
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182
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pascal@24476
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183 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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184 ;; Copy ourselves to top of memory ;;
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pascal@24476
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185 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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186
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pascal@24476
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187 mov si, 7C00h
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pascal@24476
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188 xor di, di
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pascal@24476
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189 mov ds, di
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pascal@25449
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190 push es
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pascal@25449
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191 mov [si(DriveNumber)], dx ; store BIOS boot drive number
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pascal@24478
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192 rep movsw
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pascal@24476
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193
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pascal@24476
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194 ;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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195 ;; Jump to the copy ;;
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pascal@24476
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196 ;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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197
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pascal@25486
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198 %if ExtraBootSector != 0
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pascal@25486
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199 push word main
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pascal@25486
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200 %else
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pascal@25450
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201 push byte main
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pascal@25486
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202 %endif
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pascal@25485
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203 push es
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pascal@25485
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204 pop ds
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pascal@24476
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205 retf
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pascal@24476
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206
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pascal@25486
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207 %if ExtraBootSector != 0
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pascal@25486
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208 %macro MovedCode 0
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pascal@25486
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209 %endif
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pascal@24476
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210 main:
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pascal@25449
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211 xor ebx, ebx
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pascal@25485
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212 %if ExtraBootSector != 0
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pascal@25485
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213 add al, 32
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pascal@25485
|
214 mov es, ax
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pascal@25485
|
215 mov eax, [bx(bpbHiddenSectors)]
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pascal@25485
|
216 inc eax
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pascal@25485
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217 %if LBA48bits != 0
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pascal@25485
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218 mov [bx(HiLBA)], bx
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pascal@25485
|
219 %endif
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pascal@25485
|
220 call ReadSectorBoot
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pascal@25485
|
221 push ds
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pascal@25485
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222 pop ss
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pascal@25485
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223 mov sp, 512+StackSize ; bytes 0-511 are reserved for the boot code
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pascal@25485
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224 %endif
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pascal@24476
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225
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pascal@25449
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226 %if ClusterMask != 0
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pascal@24491
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227 and byte [bx(bsRootDirectoryClusterNo+3)], 0Fh ; mask cluster value
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pascal@25449
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228 %endif
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pascal@24491
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229 mov esi, [bx(bsRootDirectoryClusterNo)] ; esi=cluster # of root dir
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pascal@24476
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230
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pascal@24478
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231 push byte ImageLoadSeg
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pascal@24478
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232 pop es
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pascal@25449
|
233
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pascal@25449
|
234 RootDirReadContinue:
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pascal@25458
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235 call ReadClusterSector ; read one sector of the root dir
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pascal@24476
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236
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pascal@24476
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237 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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238 ;; Look for the COM/EXE file to load and run ;;
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pascal@24476
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239 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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240
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pascal@24476
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241 xor di, di ; es:di -> root entries array
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pascal@24476
|
242
|
pascal@24476
|
243 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24478
|
244 ;; Looks for a file/dir by its name ;;
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pascal@24476
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245 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24478
|
246 ;; Input: DS:SI -> file name (11 chars) ;;
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pascal@24478
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247 ;; ES:DI -> root directory array ;;
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pascal@24525
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248 ;; BP = paragraphs in sector ;;
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pascal@24476
|
249 ;; Output: ESI = cluster number ;;
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pascal@24476
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250 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
|
251
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pascal@24476
|
252 FindNameCycle:
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pascal@25449
|
253 %if NullEntryCheck != 0
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pascal@24525
|
254 cmp byte [es:di], bh
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pascal@24478
|
255 je ErrFind ; end of root directory (NULL entry found)
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pascal@25449
|
256 %endif
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pascal@24478
|
257 pusha
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pascal@25454
|
258 mov cl, NameLength
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pascal@24525
|
259 mov si, ProgramName ; ds:si -> program name
|
pascal@24476
|
260 repe cmpsb
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pascal@25467
|
261 %if CheckAttrib != 0
|
pascal@25467
|
262 VolumeLabel equ 8
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pascal@25467
|
263 SubDirectory equ 10h
|
pascal@25467
|
264 jnz SkipFindName
|
pascal@25467
|
265 test byte [es:di], VolumeLabel+SubDirectory
|
pascal@25467
|
266 SkipFindName:
|
pascal@25467
|
267 %endif
|
pascal@24525
|
268 je FindNameFound
|
pascal@24478
|
269 popa
|
pascal@24525
|
270 add di, byte 32
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pascal@24476
|
271 dec bp
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pascal@24476
|
272 dec bp
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pascal@24476
|
273 jnz FindNameCycle ; next root entry
|
pascal@25458
|
274 loop RootDirReadContinue ; next sector in cluster
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pascal@25458
|
275 cmp esi, 0FFFFFF6h ; carry=0 if last cluster, and carry=1 otherwise
|
pascal@25458
|
276 jnc RootDirReadContinue ; continue to the next root dir cluster
|
pascal@24478
|
277 ErrFind:
|
pascal@24478
|
278 call Error ; end of root directory (dir end reached)
|
pascal@24476
|
279 db "File not found."
|
pascal@24476
|
280 FindNameFound:
|
pascal@24525
|
281 push word [es:di+14h-11]
|
pascal@24525
|
282 push word [es:di+1Ah-11]
|
pascal@24478
|
283 pop esi ; esi = cluster no. cx = 0
|
pascal@24476
|
284
|
pascal@24525
|
285 dec dword [es:di+1Ch-11] ; load ((n - 1)/256)*16 +1 paragraphs
|
pascal@24525
|
286 imul di, [es:di+1Ch+1-11], byte 16 ; file size in paragraphs (full pages)
|
pascal@24476
|
287
|
pascal@24476
|
288 ;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
289 ;; Load the entire file ;;
|
pascal@24476
|
290 ;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
291
|
pascal@24476
|
292 push es
|
pascal@24476
|
293 FileReadContinue:
|
pascal@24476
|
294 push di
|
pascal@25458
|
295 call ReadClusterSector ; read one sector of the boot file
|
pascal@25458
|
296 dec cx
|
pascal@24476
|
297 mov di, es
|
pascal@24478
|
298 add di, bp
|
pascal@24478
|
299 mov es, di ; es:bx updated
|
pascal@24476
|
300 pop di
|
pascal@24478
|
301
|
pascal@24476
|
302 sub di, bp
|
pascal@24476
|
303 jae FileReadContinue
|
pascal@24943
|
304 xor ax, ax
|
pascal@24476
|
305 pop bp
|
pascal@24476
|
306
|
pascal@24476
|
307 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
308 ;; Type detection, .COM or .EXE? ;;
|
pascal@24476
|
309 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
310
|
pascal@24476
|
311 mov ds, bp ; bp=ds=seg the file is loaded to
|
pascal@24535
|
312
|
pascal@24476
|
313 add bp, [bx+08h] ; bp = image base
|
pascal@24476
|
314 mov di, [bx+18h] ; di = reloc table pointer
|
pascal@24476
|
315
|
pascal@24476
|
316 cmp word [bx], 5A4Dh ; "MZ" signature?
|
pascal@24476
|
317 je RelocateEXE ; yes, it's an EXE program
|
pascal@24476
|
318
|
pascal@24476
|
319 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
320 ;; Setup and run a .COM program ;;
|
pascal@24535
|
321 ;; Set CS=DS=ES=SS SP=0 IP=100h ;;
|
pascal@25454
|
322 ;; AX=0ffffh BX=0 DX=drive and ;;
|
pascal@25454
|
323 ;; cmdline=void ;;
|
pascal@24476
|
324 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
325
|
pascal@24535
|
326 mov di, 100h ; ip
|
pascal@24476
|
327 mov bp, ImageLoadSeg-10h ; "org 100h" stuff :)
|
pascal@24476
|
328 mov ss, bp
|
pascal@24476
|
329 xor sp, sp
|
pascal@24476
|
330 push bp ; cs, ds and es
|
pascal@25486
|
331 jmp short Run
|
pascal@25485
|
332 %if ExtraBootSector != 0
|
pascal@25486
|
333 %endm
|
pascal@25485
|
334 %macro BootFileName 0
|
pascal@25485
|
335 %endif
|
pascal@24476
|
336
|
pascal@24476
|
337 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
338 ;; Relocate, setup and run a .EXE program ;;
|
pascal@24476
|
339 ;; Set CS:IP, SS:SP, DS, ES and AX according ;;
|
pascal@24476
|
340 ;; to wiki.osdev.org/MZ#Initial_Program_State ;;
|
pascal@25454
|
341 ;; AX=0ffffh BX=0 DX=drive cmdline=void ;;
|
pascal@24476
|
342 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
343
|
pascal@24476
|
344 ReloCycle:
|
pascal@24476
|
345 add [di+2], bp ; item seg (abs)
|
pascal@24476
|
346 les si, [di] ; si = item ofs, es = item seg
|
pascal@24476
|
347 add [es:si], bp ; fixup
|
pascal@24525
|
348 scasw ; di += 2
|
pascal@24525
|
349 scasw ; point to next entry
|
pascal@24476
|
350
|
pascal@24476
|
351 RelocateEXE:
|
pascal@24942
|
352 dec word [bx+06h] ; reloc items, 32768 max (128KB table)
|
pascal@24942
|
353 jns ReloCycle
|
pascal@24942
|
354
|
pascal@24945
|
355 les si, [bx+0Eh]
|
pascal@24945
|
356 add si, bp
|
pascal@24945
|
357 mov ss, si ; ss for EXE
|
pascal@24945
|
358 mov sp, es ; sp for EXE
|
pascal@24476
|
359
|
pascal@24476
|
360 lea si, [bp-10h] ; ds and es both point to the segment
|
pascal@24476
|
361 push si ; containing the PSP structure
|
pascal@24476
|
362
|
pascal@24476
|
363 add bp, [bx+16h] ; cs for EXE
|
pascal@24535
|
364 mov di, [bx+14h] ; ip for EXE
|
pascal@24476
|
365 Run:
|
pascal@24476
|
366 pop ds
|
pascal@24476
|
367 push bp
|
pascal@24535
|
368 push di
|
pascal@24476
|
369 push ds
|
pascal@24476
|
370 pop es
|
pascal@24942
|
371 mov [80h], ax ; clear cmdline
|
pascal@24942
|
372 dec ax ; both FCB in the PSP don't have a valid drive identifier
|
pascal@24476
|
373
|
pascal@24476
|
374 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
375 ;; Set the magic numbers so the program knows that it ;;
|
pascal@24476
|
376 ;; has been loaded by this bootsector and not by MS-DOS ;;
|
pascal@24476
|
377 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
378 mov si, 16381 ; prime number 2**14-3
|
pascal@24476
|
379 mov di, 32749 ; prime number 2**15-19
|
pascal@24476
|
380 mov bp, 65521 ; prime number 2**16-15
|
pascal@24476
|
381
|
pascal@24476
|
382 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
383 ;; All done, transfer control to the program now ;;
|
pascal@24476
|
384 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
385 retf
|
pascal@25485
|
386 %if ExtraBootSector != 0
|
pascal@25485
|
387 %endm
|
pascal@25485
|
388 %endif
|
pascal@24476
|
389
|
pascal@25458
|
390 ;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@25458
|
391 ;; Error Messaging Code ;;
|
pascal@25458
|
392 ;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@25458
|
393
|
pascal@25458
|
394 Error:
|
pascal@25458
|
395 pop si
|
pascal@25458
|
396 puts:
|
pascal@25458
|
397 mov ah, 0Eh
|
pascal@25458
|
398 mov bl, 7
|
pascal@25458
|
399 lodsb
|
pascal@25458
|
400 int 10h
|
pascal@25458
|
401 cmp al, '.'
|
pascal@25458
|
402 jne puts
|
pascal@25458
|
403 cbw
|
pascal@25458
|
404 int 16h ; wait for a key...
|
pascal@25458
|
405 int 19h ; bootstrap
|
pascal@25458
|
406
|
pascal@25458
|
407 Stop:
|
pascal@25458
|
408 hlt
|
pascal@25458
|
409 jmp short Stop
|
pascal@25458
|
410
|
pascal@25458
|
411 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@25458
|
412 ;; Reads a FAT32 sector ;;
|
pascal@25458
|
413 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@25458
|
414 ;; Inout: ES:BX -> buffer ;;
|
pascal@25458
|
415 ;; EAX = prev sector ;;
|
pascal@25458
|
416 ;; CX = rem sectors in cluster ;;
|
pascal@25458
|
417 ;; ESI = next cluster ;;
|
pascal@25458
|
418 ;; Output: EAX = current sector ;;
|
pascal@25458
|
419 ;; CX = rem sectors in cluster ;;
|
pascal@25458
|
420 ;; ESI = next cluster ;;
|
pascal@25458
|
421 ;; BP -> para / sector ;;
|
pascal@25458
|
422 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@25458
|
423
|
pascal@25458
|
424 ReadClusterSector:
|
pascal@25458
|
425 %if SectorOf512Bytes != 0
|
pascal@25458
|
426 mov bp, 32 ; bp = paragraphs per sector
|
pascal@25458
|
427 %else
|
pascal@24525
|
428 mov bp, [bx(bpbBytesPerSector)]
|
pascal@24525
|
429 shr bp, 4 ; bp = paragraphs per sector
|
pascal@25458
|
430 %endif
|
pascal@25449
|
431 mov dx, 1 ; adjust LBA for next sector
|
pascal@24525
|
432 inc cx
|
pascal@24525
|
433 loop ReadSectorLBA
|
pascal@24525
|
434
|
pascal@25449
|
435 mul ebx ; edx:eax = 0
|
pascal@25458
|
436 %if SectorOf512Bytes != 0
|
pascal@25458
|
437 mov al, 128 ; ax=# of FAT32 entries per sector
|
pascal@25458
|
438 %else
|
pascal@24945
|
439 imul ax, bp, byte 4 ; ax=# of FAT32 entries per sector
|
pascal@25458
|
440 %endif
|
pascal@24525
|
441 lea edi, [esi-2] ; esi=cluster #
|
pascal@24476
|
442 xchg eax, esi
|
pascal@24478
|
443 div esi ; eax=FAT sector #, edx=entry # in sector
|
pascal@24476
|
444
|
pascal@24525
|
445 imul si, dx, byte 4 ; si=entry # in sector, clear C
|
pascal@25485
|
446 %if NonMirroredFATs != 0
|
pascal@25485
|
447 cwde
|
pascal@25485
|
448 or dl, byte [bx(bsExtendedFlags)]
|
pascal@25485
|
449 jns MirroredFATs ; Non-mirrored FATs ?
|
pascal@25485
|
450 and dl, 0Fh
|
pascal@25485
|
451 imul edx, dword [bx(bsSectorsPerFAT32)] ; we need to read the active one
|
pascal@25485
|
452 add eax, edx
|
pascal@25485
|
453 MirroredFATs:
|
pascal@25485
|
454 cwde
|
pascal@25485
|
455 %else
|
pascal@25485
|
456 %if LBA48bits != 0
|
pascal@25458
|
457 xor dx, dx
|
pascal@25485
|
458 %endif
|
pascal@25449
|
459 %endif
|
pascal@25458
|
460 call ReadSectorLBAfromFAT ; read 1 FAT32 sector
|
pascal@24476
|
461
|
pascal@25449
|
462 %if ClusterMask != 0
|
pascal@24478
|
463 and byte [es:si+3], 0Fh ; mask cluster value
|
pascal@25449
|
464 %endif
|
pascal@24478
|
465 mov esi, [es:si] ; esi=next cluster #
|
pascal@24476
|
466
|
pascal@25458
|
467 %if Always2FATs != 0
|
pascal@25458
|
468 imul eax, dword [bx(bsSectorsPerFAT32)], 2
|
pascal@25458
|
469 %else
|
pascal@24525
|
470 movzx eax, byte [bx(bpbNumberOfFATs)]
|
pascal@24525
|
471 mul dword [bx(bsSectorsPerFAT32)]
|
pascal@25458
|
472 %endif
|
pascal@24525
|
473
|
pascal@24525
|
474 xchg eax, edi
|
pascal@25454
|
475 movzx ecx, byte [bx(bpbSectorsPerCluster)] ; 8..128
|
pascal@24945
|
476 mul ecx ; edx:eax=sector number in data area
|
pascal@24525
|
477 add eax, edi
|
pascal@25458
|
478 %if LBA48bits != 0
|
pascal@25458
|
479 adc dx, bx
|
pascal@25458
|
480 %endif
|
pascal@24476
|
481
|
pascal@25458
|
482 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@25458
|
483 ;; Reads a sector form the start of FAT ;;
|
pascal@25458
|
484 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@25458
|
485
|
pascal@25458
|
486 ReadSectorLBAfromFAT:
|
pascal@25458
|
487 add eax, [bx(bpbHiddenSectors)]
|
pascal@25449
|
488 %if LBA48bits != 0
|
pascal@25449
|
489 adc dx, bx
|
pascal@25449
|
490 mov word [bx(HiLBA)], dx
|
pascal@25449
|
491 %endif
|
pascal@25454
|
492 mov dx, [bx(bpbReservedSectors)]
|
pascal@24476
|
493
|
pascal@24478
|
494 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24478
|
495 ;; Reads a sector using BIOS Int 13h fn 42h ;;
|
pascal@24478
|
496 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24478
|
497 ;; Input: EAX = LBA ;;
|
pascal@24478
|
498 ;; CX = sector count ;;
|
pascal@24478
|
499 ;; ES:BX -> buffer address ;;
|
pascal@24478
|
500 ;; Output: CF = 0 if no more sectors ;;
|
pascal@24478
|
501 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
502
|
pascal@24476
|
503 ReadSectorLBA:
|
pascal@25449
|
504 add eax, edx
|
pascal@25449
|
505 %if LBA48bits != 0
|
pascal@24535
|
506 adc word [bx(HiLBA)], bx
|
pascal@25449
|
507 %endif
|
pascal@25485
|
508 ReadSectorBoot:
|
pascal@25449
|
509 mov dx, [bx(DriveNumber)] ; restore BIOS boot drive number
|
pascal@24476
|
510 pusha
|
pascal@24476
|
511
|
pascal@24478
|
512 push bx
|
pascal@25449
|
513 %if LBA48bits != 0
|
pascal@24491
|
514 push word [bx(HiLBA)] ; 48-bit LBA
|
pascal@25449
|
515 %else
|
pascal@25449
|
516 push bx
|
pascal@25449
|
517 %endif
|
pascal@24478
|
518 push eax
|
pascal@24476
|
519 push es
|
pascal@24476
|
520 push bx
|
pascal@24478
|
521 push byte 1 ; sector count word = 1
|
pascal@24525
|
522 push byte 16 ; packet size byte = 16, reserved byte = 0
|
pascal@24525
|
523
|
pascal@25449
|
524 %if CHSsupport != 0
|
pascal@25458
|
525 %if CHSupTo8GB != 0
|
pascal@25449
|
526 push eax
|
pascal@25449
|
527 pop cx ; save low LBA
|
pascal@25449
|
528 pop ax ; get high LBA
|
pascal@25449
|
529 cwd ; clear dx (assume LBA offset <1TB)
|
pascal@25449
|
530 idiv word [bx(bpbSectorsPerTrack)] ; up to 8GB disks, avoid divide error
|
pascal@25449
|
531
|
pascal@25449
|
532 xchg ax, cx ; restore low LBA, save high LBA / SPT
|
pascal@25458
|
533 %else
|
pascal@25449
|
534 ; Busybox mkdosfs creates fat32 for floppies.
|
pascal@25449
|
535 ; Floppies may support CHS only.
|
pascal@25458
|
536 %if CHSupTo32MB != 0
|
pascal@25458
|
537 xor dx, dx ; clear dx (LBA offset <32MB)
|
pascal@25458
|
538 %else
|
pascal@25449
|
539 cwd ; clear dx (LBA offset <16MB)
|
pascal@25458
|
540 %endif
|
pascal@25450
|
541 xor cx, cx ; high LBA / SPT = 0
|
pascal@25458
|
542 %endif
|
pascal@25449
|
543 idiv word [bx(bpbSectorsPerTrack)]
|
pascal@25449
|
544 ; ax = LBA / SPT
|
pascal@25449
|
545 ; dx = LBA % SPT = sector - 1
|
pascal@25449
|
546 inc dx
|
pascal@25449
|
547
|
pascal@25449
|
548 xchg cx, dx ; restore high LBA / SPT, save sector no.
|
pascal@25450
|
549 idiv word [bx(bpbHeadsPerCylinder)]
|
pascal@25449
|
550 ; ax = (LBA / SPT) / HPC = cylinder
|
pascal@25449
|
551 ; dx = (LBA / SPT) % HPC = head
|
pascal@25449
|
552
|
pascal@25458
|
553 xchg ch, al ; clear al
|
pascal@25449
|
554 ; ch = LSB 0...7 of cylinder no.
|
pascal@25458
|
555 %if CHSupTo8GB != 0 || CHSupTo32MB != 0
|
pascal@25458
|
556 shr ax, 2
|
pascal@25458
|
557 or cl, al
|
pascal@25449
|
558 ; cl = MSB 8...9 of cylinder no. + sector no.
|
pascal@25458
|
559 %endif
|
pascal@25449
|
560 mov dh, dl
|
pascal@25449
|
561 ; dh = head no.
|
pascal@25449
|
562 mov dl, [bx(DriveNumber)] ; restore BIOS boot drive number
|
pascal@25449
|
563 %endif
|
pascal@25449
|
564
|
pascal@25454
|
565 ReadSectorRetry:
|
pascal@24525
|
566 mov si, sp
|
pascal@24478
|
567 mov ah, 42h ; ah = 42h = extended read function no.
|
pascal@24478
|
568 int 13h ; extended read sectors (DL, DS:SI)
|
pascal@24478
|
569 jnc ReadSuccess ; CF = 0 if no error
|
pascal@24476
|
570
|
pascal@25449
|
571 %if CHSsupport != 0
|
pascal@25449
|
572 mov ax, 201h ; al = sector count = 1
|
pascal@25449
|
573 ; ah = 2 = read function no.
|
pascal@25449
|
574 int 13h ; read sectors (AL, CX, DX, ES:BX)
|
pascal@25449
|
575
|
pascal@25449
|
576 jnc ReadSuccess ; CF = 0 if no error
|
pascal@25449
|
577 %endif
|
pascal@25449
|
578 %if ReadRetry != 0
|
pascal@25458
|
579 %if CHSsupport != 0
|
pascal@25449
|
580 cbw ; ah = 0 = reset function
|
pascal@25458
|
581 %else
|
pascal@24945
|
582 xor ax, ax ; ah = 0 = reset function
|
pascal@25458
|
583 %endif
|
pascal@24476
|
584 int 13h ; reset drive (DL)
|
pascal@24476
|
585
|
pascal@25457
|
586 dec bp ; up to 32 retries
|
pascal@25454
|
587 jnz ReadSectorRetry
|
pascal@25449
|
588 %endif
|
pascal@24525
|
589
|
pascal@24476
|
590 call Error
|
pascal@24476
|
591 db "Read error."
|
pascal@24476
|
592
|
pascal@24478
|
593 ReadSuccess:
|
pascal@24476
|
594
|
pascal@24476
|
595 popa ; sp += 16
|
pascal@24478
|
596 popa
|
pascal@24476
|
597 ret
|
pascal@24476
|
598
|
pascal@25486
|
599 %if ExtraBootSector != 0
|
pascal@25486
|
600 MovedCode
|
pascal@25486
|
601 %endif
|
pascal@25486
|
602
|
pascal@24942
|
603 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24942
|
604 ;; Fill free space with zeroes ;;
|
pascal@24942
|
605 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24942
|
606
|
pascal@25458
|
607 times (512-13-($-$$)) db 0
|
pascal@24476
|
608
|
pascal@24476
|
609 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
610 ;; Name of the file to load and run ;;
|
pascal@24476
|
611 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
612
|
pascal@25463
|
613 NameLength equ 11
|
pascal@25463
|
614 ProgramName times NameLength db 0 ; name and extension
|
pascal@24476
|
615
|
pascal@24476
|
616 ;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
617 ;; End of the sector ID ;;
|
pascal@24476
|
618 ;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
619
|
pascal@24476
|
620 dw 0AA55h ; BIOS checks for this ID
|
pascal@25485
|
621
|
pascal@25485
|
622 %if ExtraBootSector != 0
|
pascal@25485
|
623 dd 61415252h ; "RRaA"
|
pascal@25485
|
624 BootFileName
|
pascal@25485
|
625 times (996-($-$$)) db 0
|
pascal@25485
|
626 ; dd 41617272h ; "rrAa"
|
pascal@25485
|
627 %endif
|