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pascal@24476
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1 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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2 ;; ;;
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pascal@24476
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3 ;; "BootProg" Loader v 1.5 by Alexey Frunze (c) 2000-2015 ;;
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pascal@24476
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4 ;; 2-clause BSD license. ;;
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pascal@24476
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5 ;; ;;
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pascal@24476
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6 ;; ;;
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pascal@24476
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7 ;; How to Compile: ;;
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pascal@24476
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8 ;; ~~~~~~~~~~~~~~~ ;;
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pascal@24476
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9 ;; nasm boot16.asm -f bin -o boot16.bin ;;
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pascal@24476
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10 ;; ;;
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pascal@24476
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11 ;; ;;
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pascal@24476
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12 ;; Features: ;;
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pascal@24476
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13 ;; ~~~~~~~~~ ;;
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pascal@24476
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14 ;; - FAT12 and FAT16 supported using BIOS int 13h function 42h or 02h. ;;
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pascal@24476
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15 ;; ;;
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pascal@24476
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16 ;; - Loads a 16-bit executable file in the MS-DOS .COM or .EXE format ;;
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pascal@24476
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17 ;; from the root directory of a disk and transfers control to it ;;
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pascal@24476
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18 ;; (the "ProgramName" variable holds the name of the file to be loaded) ;;
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pascal@24476
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19 ;; Its maximum size can be up to 635KB without Extended BIOS Data area. ;;
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pascal@24476
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20 ;; ;;
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pascal@24476
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21 ;; - Prints an error if the file isn't found or couldn't be read ;;
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pascal@24476
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22 ;; ("File not found" or "Read error") ;;
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pascal@24476
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23 ;; and waits for a key to be pressed, then executes the Int 19h ;;
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pascal@24476
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24 ;; instruction and lets the BIOS continue bootstrap. ;;
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pascal@24476
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25 ;; ;;
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pascal@24476
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26 ;; - cpu 8086 is supported ;;
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pascal@24476
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27 ;; ;;
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pascal@24476
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28 ;; ;;
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pascal@25564
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29 ;; Known Limitation: ;;
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pascal@25564
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30 ;; ~~~~~~~~~~~~~~~~~ ;;
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pascal@25564
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31 ;; - Need a up to date field bpbHiddenSectors to work in a partition ; ;;
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pascal@25564
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32 ;; most formatters don't update it correcly in extended partitions. ;;
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pascal@25564
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33 ;; ;;
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pascal@25564
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34 ;; - Partition must fit in the first 8GB disk for CHS reads. ;;
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pascal@25564
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35 ;; ;;
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pascal@25564
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36 ;; ;;
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pascal@24476
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37 ;; Known Bugs: ;;
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pascal@24476
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38 ;; ~~~~~~~~~~~ ;;
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pascal@24476
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39 ;; - 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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40 ;; on the following types of diskettes (FAT12): ;;
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pascal@24476
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41 ;; - 360KB 5"25 ;;
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pascal@24476
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42 ;; - 1.2MB 5"25 ;;
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pascal@24476
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43 ;; - 1.44MB 3"5 ;;
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pascal@24476
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44 ;; on my HDD (FAT16). ;;
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pascal@24476
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45 ;; ;;
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pascal@24476
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46 ;; ;;
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pascal@24476
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47 ;; Memory Layout: ;;
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pascal@24476
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48 ;; ~~~~~~~~~~~~~~ ;;
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pascal@24476
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49 ;; The diagram below shows the typical memory layout. The actual location ;;
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pascal@24476
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50 ;; 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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51 ;; reserves memory for its Extended BIOS Data Area just below A0000H and ;;
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pascal@24476
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52 ;; reports less than 640 KB of RAM via its Int 12H function. ;;
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pascal@24476
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53 ;; ;;
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pascal@24476
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54 ;; physical address ;;
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pascal@24476
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55 ;; +------------------------+ 00000H ;;
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pascal@24476
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56 ;; | Interrupt Vector Table | ;;
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pascal@24476
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57 ;; +------------------------+ 00400H ;;
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pascal@24476
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58 ;; | BIOS Data Area | ;;
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pascal@24476
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59 ;; +------------------------+ 00500H ;;
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pascal@24476
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60 ;; | PrtScr Status / Unused | ;;
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pascal@24476
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61 ;; +------------------------+ 00600H ;;
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pascal@24476
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62 ;; | Loaded Image | ;;
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pascal@24476
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63 ;; +------------------------+ nnnnnH ;;
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pascal@24476
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64 ;; | Available Memory | ;;
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pascal@24476
|
65 ;; +------------------------+ A0000H - 512 - 3KB ;;
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pascal@24476
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66 ;; | Boot Sector | ;;
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pascal@24476
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67 ;; +------------------------+ A0000H - 3KB ;;
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pascal@24476
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68 ;; | 3KB Boot Stack | ;;
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pascal@24476
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69 ;; +------------------------+ A0000H ;;
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pascal@24476
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70 ;; | Video RAM | ;;
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pascal@24476
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71 ;; ;;
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pascal@24476
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72 ;; ;;
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pascal@24476
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73 ;; Boot Image Startup (register values): ;;
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pascal@24476
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74 ;; ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ;;
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pascal@24945
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75 ;; ax = 0ffffh (both FCB in the PSP don't have a valid drive identifier), ;;
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pascal@25454
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76 ;; bx = 0, dl = BIOS boot drive number (e.g. 0, 80H) ;;
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pascal@24476
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77 ;; cs:ip = program entry point ;;
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pascal@24476
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78 ;; ss:sp = program stack (don't confuse with boot sector's stack) ;;
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pascal@24476
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79 ;; COM program defaults: cs = ds = es = ss = 50h, sp = 0, ip = 100h ;;
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pascal@24476
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80 ;; EXE program defaults: ds = es = EXE data - 10h (fake MS-DOS psp), ;;
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pascal@24476
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81 ;; cs:ip and ss:sp depends on EXE header ;;
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pascal@24476
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82 ;; Magic numbers: ;;
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pascal@24476
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83 ;; si = 16381 (prime number 2**14-3) ;;
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pascal@24476
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84 ;; di = 32749 (prime number 2**15-19) ;;
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pascal@24476
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85 ;; bp = 65521 (prime number 2**16-15) ;;
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pascal@24476
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86 ;; The magic numbers let the program know whether it has been loaded by ;;
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pascal@24476
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87 ;; this boot sector or by MS-DOS, which may be handy for universal, bare- ;;
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pascal@24476
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88 ;; metal and MS-DOS programs. ;;
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pascal@24945
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89 ;; The command line contains no arguments. ;;
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pascal@24476
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90 ;; ;;
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pascal@24476
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91 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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92
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pascal@24476
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93 %define bx(label) bx+label-boot
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pascal@25450
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94 %define si(label) si+label-boot
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pascal@25458
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95 NullEntryCheck equ 1 ; +2 bytes
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pascal@25564
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96 ReadRetry equ 1 ; +9/+10 bytes
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pascal@25450
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97 LBAsupport equ 1 ; +16 bytes
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pascal@25564
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98 CHSsanityCheck equ 1 ; +12/+16 bytes
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pascal@25450
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99 GeometryCheck equ 1 ; +18 bytes
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pascal@25564
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100 CheckAttrib equ 0 ; +6 bytes
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pascal@25564
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101 WaitForKey equ 0 ; +5 bytes
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pascal@25550
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102 SectorOf512Bytes equ 0 ; -4/-6 bytes
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pascal@25564
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103 Always2FATs equ 0 ; -1 bytes
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pascal@24476
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104
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pascal@24476
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105 [BITS 16]
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pascal@24476
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106 [CPU 8086]
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pascal@24476
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107
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pascal@24476
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108 ImageLoadSeg equ 60h
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pascal@24476
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109 StackSize equ 3072 ; Stack + cluster list
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pascal@24476
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110
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pascal@24476
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111 [SECTION .text]
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pascal@24476
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112 [ORG 0]
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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 ;; Boot sector 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@24476
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118 boot:
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pascal@25450
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119 DriveNumber:
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pascal@24476
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120 jmp short start ; MS-DOS/Windows checks for this jump
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pascal@24476
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121 nop
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pascal@24476
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122 bsOemName DB "BootProg" ; 0x03
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pascal@24476
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123
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pascal@24476
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124 ;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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125 ;; BPB starts here ;;
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pascal@24476
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126 ;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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127
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pascal@25564
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128 bpbBytesPerSector DW 0 ; 0x0B 512, 1024, 2048 or 4096
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pascal@25564
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129 bpbSectorsPerCluster DB 0 ; 0x0D 1, 2, 4, 8, 16, 32 or 64
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pascal@25564
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130 bpbReservedSectors DW 0 ; 0x0E 1
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pascal@25564
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131 bpbNumberOfFATs DB 0 ; 0x10 2
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pascal@24479
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132 bpbRootEntries DW 0 ; 0x11
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pascal@24479
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133 bpbTotalSectors DW 0 ; 0x13
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pascal@24479
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134 bpbMedia DB 0 ; 0x15
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pascal@24479
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135 bpbSectorsPerFAT DW 0 ; 0x16
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pascal@24479
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136 bpbSectorsPerTrack DW 0 ; 0x18
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pascal@24479
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137 bpbHeadsPerCylinder DW 0 ; 0x1A
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pascal@24479
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138 bpbHiddenSectors DD 0 ; 0x1C
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pascal@24479
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139 bpbTotalSectorsBig DD 0 ; 0x20
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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 ;; BPB ends here ;;
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pascal@24476
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143 ;;;;;;;;;;;;;;;;;;;
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pascal@24476
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144
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pascal@24479
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145 bsDriveNumber DB 0 ; 0x24
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pascal@24479
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146 bsUnused DB 0 ; 0x25
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pascal@25564
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147 bsExtBootSignature DB 0 ; 0x26 29
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pascal@24479
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148 bsSerialNumber DD 0 ; 0x27
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pascal@25458
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149 bsVolumeLabel times 11 DB " " ; 0x2B "NO NAME "
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pascal@25458
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150 bsFileSystem times 8 DB " " ; 0x36 "FAT12 " or "FAT16 "
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pascal@24476
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151
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pascal@24476
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152 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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153 ;; Boot sector code starts here ;;
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pascal@24476
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154 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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155
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pascal@24476
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156 start:
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pascal@24476
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157 cld
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pascal@24476
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158
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pascal@24476
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159 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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160 ;; How much RAM is there? ;;
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pascal@24476
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161 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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162
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pascal@24476
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163 int 12h ; get conventional memory size (in KBs)
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pascal@24476
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164 mov cx, 106h
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pascal@24476
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165 shl ax, cl ; and convert it to 16-byte paragraphs
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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 ;; Reserve memory for the boot sector and its stack ;;
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pascal@24476
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169 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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170
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pascal@24476
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171 sub ax, (512+StackSize) /16 ; reserve bytes for the code and the stack
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pascal@24476
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172 mov es, ax ; cs:0 = ds:0 = ss:0 -> top - 512 - StackSize
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pascal@24476
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173 mov ss, ax
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pascal@24476
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174 mov sp, 512+StackSize ; bytes 0-511 are reserved for the boot code
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pascal@24476
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175
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pascal@24476
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176 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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177 ;; Copy ourselves to top of memory ;;
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pascal@24476
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178 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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179
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pascal@24476
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180 mov si, 7C00h
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pascal@24476
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181 xor di, di
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pascal@24476
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182 mov ds, di
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pascal@25450
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183 push es
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pascal@25450
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184 mov [si(DriveNumber)], dx ; store BIOS boot drive number
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pascal@24476
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185 rep movsw ; move 512 bytes (+ 12)
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pascal@24476
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186
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pascal@24476
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187 ;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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188 ;; Jump to the copy ;;
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pascal@24476
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189 ;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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190
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pascal@24476
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191 mov cl, byte main
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pascal@24476
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192 push cx
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pascal@24476
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193 retf
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pascal@24476
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194
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pascal@24476
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195 main:
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pascal@24476
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196 %if ImageLoadSeg != main-boot
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pascal@24476
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197 %if ImageLoadSeg >= 100h
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pascal@24476
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198 mov cx, ImageLoadSeg
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pascal@24476
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199 %else
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pascal@24476
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200 mov cl, ImageLoadSeg
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pascal@24476
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201 %endif
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pascal@24476
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202 %endif
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pascal@24476
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203 push cx
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pascal@24476
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204
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pascal@24476
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205 ;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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206 ;; Get drive parameters ;;
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pascal@24476
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207 ;; Update heads count ;;
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pascal@24476
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208 ;; for current BIOS ;;
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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@25450
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211 %if GeometryCheck != 0
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pascal@25564
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212 %if ((main-boot) & 3Fh) != 0
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pascal@25564
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213 xchg ax, cx ; ax & 3Fh == 0
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pascal@25564
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214 %endif
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pascal@25564
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215 mov ah, 8 ; update AX,BL,CX,DX,DI, and ES registers
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pascal@24476
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216 int 13h ; may destroy SI,BP, and DS registers
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pascal@25450
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217 %endif
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pascal@24476
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218 push cs
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pascal@24476
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219 pop ds
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pascal@24476
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220 xor bx, bx
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pascal@24476
|
221
|
pascal@25450
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222 %if GeometryCheck != 0
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pascal@24479
|
223 and cx, byte 3Fh
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pascal@25564
|
224 je BadParams ; verify updated and validity
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pascal@25564
|
225 mov [bx(bpbSectorsPerTrack)], cx
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pascal@25564
|
226 mov cl, dh
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pascal@25564
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227 inc cx
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pascal@25564
|
228 mov [bx(bpbHeadsPerCylinder)], cx
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pascal@24476
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229 BadParams:
|
pascal@25450
|
230 %endif
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pascal@24476
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231
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pascal@24476
|
232 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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233 ;; Load FAT (FAT12: 6KB max, FAT16: 128KB max) ;;
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pascal@24476
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234 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
|
235
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pascal@24476
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236 pop es ; ImageLoadSeg
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pascal@24476
|
237 push es
|
pascal@24476
|
238
|
pascal@24476
|
239 mul bx ; dx:ax = 0 = LBA (LBA are relative to FAT)
|
pascal@25458
|
240 mov di, word [bx(bpbSectorsPerFAT)]
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pascal@24476
|
241
|
pascal@25458
|
242 call ReadDISectors ; read fat; clear ax, cx, di; bp = SectorsPerFAT
|
pascal@24476
|
243
|
pascal@24476
|
244 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
245 ;; load the root directory in ;;
|
pascal@24476
|
246 ;; its entirety (16KB max) ;;
|
pascal@24476
|
247 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
248
|
pascal@25458
|
249 %if SectorOf512Bytes != 0
|
pascal@25458
|
250 mov di, word [bx(bpbRootEntries)]
|
pascal@25458
|
251 mov cl, 4
|
pascal@25458
|
252 shr di, cl ; di = root directory size in sectors
|
pascal@25458
|
253 %else
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pascal@24942
|
254 mov al, 32
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pascal@24476
|
255
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pascal@24476
|
256 mul word [bx(bpbRootEntries)]
|
pascal@24476
|
257 div word [bx(bpbBytesPerSector)]
|
pascal@25458
|
258 xchg ax, di ; di = root directory size in sectors, clear ah
|
pascal@25458
|
259 %endif
|
pascal@24476
|
260
|
pascal@25564
|
261 %if Always2FATs != 0
|
pascal@25564
|
262 mov al, 2
|
pascal@25564
|
263 %else
|
pascal@24476
|
264 mov al, [bpbNumberOfFATs]
|
pascal@25564
|
265 %endif
|
pascal@25458
|
266 mul bp ; [bx(bpbSectorsPerFAT)], set by ReadDISectors
|
pascal@24476
|
267
|
pascal@25457
|
268 push es ; read root directory
|
pascal@25458
|
269 call ReadDISectors ; clear ax, cx, di; bp = first data sector
|
pascal@24476
|
270 pop es
|
pascal@24476
|
271
|
pascal@24476
|
272 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
273 ;; Look for the COM/EXE file to load and run ;;
|
pascal@24476
|
274 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
275
|
pascal@24476
|
276 ; es:di -> root entries array
|
pascal@24476
|
277
|
pascal@24476
|
278 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
279 ;; Looks for the file/dir ProgramName ;;
|
pascal@24476
|
280 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
281 ;; Input: ES:DI -> root directory array ;;
|
pascal@24476
|
282 ;; Output: SI = cluster number ;;
|
pascal@24476
|
283 ;; AX = file sector count ;;
|
pascal@24476
|
284 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
285
|
pascal@24476
|
286 FindNameCycle:
|
pascal@24476
|
287 push di
|
pascal@25454
|
288 mov cl, NameLength
|
pascal@24476
|
289 mov si, ProgramName ; ds:si -> program name
|
pascal@24476
|
290 repe cmpsb
|
pascal@25467
|
291 %if CheckAttrib != 0
|
pascal@25467
|
292 VolumeLabel equ 8
|
pascal@25467
|
293 SubDirectory equ 10h
|
pascal@25467
|
294 jnz SkipFindName
|
pascal@25467
|
295 test byte [es:di], VolumeLabel+SubDirectory
|
pascal@25467
|
296 SkipFindName:
|
pascal@25467
|
297 %endif
|
pascal@24476
|
298 pop di
|
pascal@24476
|
299 je FindNameFound
|
pascal@25450
|
300 %if NullEntryCheck != 0
|
pascal@25564
|
301 scasb ; Z == NC
|
pascal@25458
|
302 cmc
|
pascal@25458
|
303 lea di, [di+31]
|
pascal@25458
|
304 dec word [bx(bpbRootEntries)]
|
pascal@25458
|
305 ja FindNameCycle ; next root entry
|
pascal@25450
|
306 %else
|
pascal@25450
|
307 add di, byte 32
|
pascal@24476
|
308 dec word [bx(bpbRootEntries)]
|
pascal@24476
|
309 jnz FindNameCycle ; next root entry
|
pascal@25458
|
310 %endif
|
pascal@24476
|
311
|
pascal@24476
|
312 FindNameFailed:
|
pascal@24476
|
313 call Error
|
pascal@24476
|
314 db "File not found."
|
pascal@24476
|
315
|
pascal@24476
|
316 FindNameFound:
|
pascal@24476
|
317 push si
|
pascal@24476
|
318 mov si, [es:di+1Ah] ; si = cluster no.
|
pascal@24476
|
319 les ax, [es:di+1Ch] ; file size
|
pascal@24476
|
320 mov dx, es
|
pascal@24476
|
321 div word [bx(bpbBytesPerSector)]
|
pascal@24476
|
322 cmp bx, dx ; sector aligned ?
|
pascal@24476
|
323 adc ax, bx ; file last sector
|
pascal@24476
|
324 pop di ; di = ClusterList
|
pascal@24476
|
325
|
pascal@24476
|
326 pop es ; ImageLoadSeg
|
pascal@24476
|
327 push ax
|
pascal@24476
|
328
|
pascal@24476
|
329 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
330 ;; build cluster list ;;
|
pascal@24476
|
331 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
332 ;; Input: ES:0 -> FAT ;;
|
pascal@24476
|
333 ;; SI = first cluster ;;
|
pascal@24476
|
334 ;; DI = cluster list :;
|
pascal@24476
|
335 ;; CH = 0 ;;
|
pascal@24476
|
336 ;; Output: SI = cluster list ;;
|
pascal@24476
|
337 ;; CH = 0 ;;
|
pascal@24476
|
338 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
339
|
pascal@25458
|
340 FAT12 equ 1
|
pascal@25458
|
341 FAT16 equ 1
|
pascal@25550
|
342 TINYFAT16 equ 1 ; < 4072 clusters fat16 support
|
pascal@25453
|
343 push di ; up to 2 * 635K / BytesPerCluster = 2540 bytes
|
pascal@25450
|
344 %if FAT12 == 1
|
pascal@25454
|
345 mov cl, 12
|
pascal@25564
|
346 %else
|
pascal@25564
|
347 nop
|
pascal@25564
|
348 nop
|
pascal@25450
|
349 %endif
|
pascal@24476
|
350 ClusterLoop:
|
pascal@24476
|
351 mov [di], si
|
pascal@25450
|
352 add si, si ; si = cluster * 2
|
pascal@25450
|
353 %if FAT16 == 1
|
pascal@24476
|
354 mov ax, es ; ax = FAT segment = ImageLoadSeg
|
pascal@25094
|
355 jnc First64k
|
pascal@24476
|
356 mov ah, (1000h+ImageLoadSeg)>>8 ; adjust segment for 2nd part of FAT16
|
pascal@25094
|
357 First64k:
|
pascal@25453
|
358 %if FAT12 == 1
|
pascal@25457
|
359 mov dx, 0FFF6h
|
pascal@25454
|
360 %if TINYFAT16 == 1
|
pascal@25550
|
361 test [bx(bsFileSystem+4)], cl ; FAT12 or FAT16 ? clear C (bit 2)
|
pascal@25458
|
362 jne ReadClusterFat16
|
pascal@25454
|
363 %else
|
pascal@25454
|
364 cmp [bx(bpbSectorsPerFAT)], cx ; 1..12 = FAT12, 16..256 = FAT16
|
pascal@25458
|
365 ja ReadClusterFat16
|
pascal@25454
|
366 %endif
|
pascal@24942
|
367 mov dh, 0Fh
|
pascal@25453
|
368 %endif
|
pascal@25450
|
369 %endif
|
pascal@25450
|
370 %if FAT12 == 1
|
pascal@25087
|
371 add si, [di]
|
pascal@24476
|
372 shr si, 1 ; si = cluster * 3 / 2
|
pascal@25564
|
373 %else
|
pascal@25564
|
374 nop
|
pascal@25564
|
375 nop
|
pascal@25450
|
376 %endif
|
pascal@25450
|
377 %if FAT16 == 1
|
pascal@24942
|
378 ReadClusterFat16:
|
pascal@25094
|
379 push ds
|
pascal@25087
|
380 mov ds, ax
|
pascal@24476
|
381 lodsw ; ax = next cluster
|
pascal@25094
|
382 pop ds
|
pascal@25450
|
383 %else
|
pascal@25453
|
384 es lodsw
|
pascal@25450
|
385 %endif
|
pascal@25450
|
386 %if FAT12 == 1
|
pascal@24476
|
387 jnc ReadClusterEven
|
pascal@25454
|
388 rol ax, cl
|
pascal@24476
|
389 ReadClusterEven:
|
pascal@25094
|
390 scasw ; di += 2
|
pascal@25454
|
391 %if FAT16 == 1
|
pascal@24942
|
392 and ah, dh ; mask cluster value
|
pascal@24942
|
393 cmp ax, dx
|
pascal@25454
|
394 %else
|
pascal@25453
|
395 and ah, 0Fh ; mask cluster value
|
pascal@25457
|
396 cmp ax, 0FF6h
|
pascal@25454
|
397 %endif
|
pascal@25454
|
398 %else
|
pascal@25454
|
399 scasw ; di += 2
|
pascal@25457
|
400 cmp ax, 0FFF6h
|
pascal@25453
|
401 %endif
|
pascal@24476
|
402 xchg ax, si
|
pascal@24476
|
403 jc ClusterLoop
|
pascal@24476
|
404 pop si
|
pascal@24476
|
405 pop di ; file size in sectors
|
pascal@24476
|
406
|
pascal@24476
|
407 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
408 ;; Load the entire file ;;
|
pascal@24476
|
409 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
410 ;; Input: ES:0 -> buffer ;;
|
pascal@24476
|
411 ;; SI = cluster list ;;
|
pascal@24476
|
412 ;; DI = file sectors ;;
|
pascal@24476
|
413 ;; CH = 0 ;;
|
pascal@24945
|
414 ;; BP = 1st data sec ;;
|
pascal@24476
|
415 ;; Output: BP:0 -> buffer ;;
|
pascal@24476
|
416 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
417
|
pascal@24476
|
418 push es
|
pascal@24476
|
419
|
pascal@24476
|
420 ReadClusters:
|
pascal@24476
|
421 lodsw
|
pascal@24476
|
422 dec ax
|
pascal@24476
|
423 dec ax
|
pascal@24476
|
424
|
pascal@25454
|
425 mov cl, [bx(bpbSectorsPerCluster)] ; 1..128
|
pascal@24476
|
426 mul cx ; cx = sector count (ch = 0)
|
pascal@24476
|
427
|
pascal@24476
|
428 add ax, bp ; LBA for cluster data
|
pascal@24476
|
429 adc dx, bx ; dx:ax = LBA
|
pascal@24476
|
430
|
pascal@25458
|
431 call ReadSectors ; clear ax, restore dx
|
pascal@24476
|
432
|
pascal@25458
|
433 jne ReadClusters ; until end of file
|
pascal@24476
|
434
|
pascal@24476
|
435 pop bp ; ImageLoadSeg
|
pascal@24476
|
436
|
pascal@24476
|
437 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
438 ;; Type detection, .COM or .EXE? ;;
|
pascal@24476
|
439 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
440
|
pascal@24476
|
441 mov ds, bp ; bp=ds=seg the file is loaded to
|
pascal@24476
|
442
|
pascal@24476
|
443 add bp, [bx+08h] ; bp = image base
|
pascal@24476
|
444 mov di, [bx+18h] ; di = reloc table pointer
|
pascal@24476
|
445
|
pascal@24476
|
446 cmp word [bx], 5A4Dh ; "MZ" signature?
|
pascal@24476
|
447 je RelocateEXE ; yes, it's an EXE program
|
pascal@24476
|
448
|
pascal@24476
|
449 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
450 ;; Setup and run a .COM program ;;
|
pascal@24476
|
451 ;; Set CS=DS=ES=SS SP=0 IP=100h ;;
|
pascal@25454
|
452 ;; AX=0ffffh BX=0 DX=drive and ;;
|
pascal@25454
|
453 ;; cmdline=void ;;
|
pascal@24476
|
454 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
455
|
pascal@24942
|
456 mov di, 100h ; ip
|
pascal@24476
|
457 mov bp, ImageLoadSeg-10h ; "org 100h" stuff :)
|
pascal@24476
|
458 mov ss, bp
|
pascal@24476
|
459 xor sp, sp
|
pascal@24476
|
460 push bp ; cs, ds and es
|
pascal@24476
|
461 jmp short Run
|
pascal@24476
|
462
|
pascal@24476
|
463 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
464 ;; Relocate, setup and run a .EXE program ;;
|
pascal@24476
|
465 ;; Set CS:IP, SS:SP, DS, ES and AX according ;;
|
pascal@24476
|
466 ;; to wiki.osdev.org/MZ#Initial_Program_State ;;
|
pascal@25454
|
467 ;; AX=0ffffh BX=0 DX=drive cmdline=void ;;
|
pascal@24476
|
468 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
469
|
pascal@24476
|
470 ReloCycle:
|
pascal@24476
|
471 add [di+2], bp ; item seg (abs)
|
pascal@24476
|
472 les si, [di] ; si = item ofs, es = item seg
|
pascal@24476
|
473 add [es:si], bp ; fixup
|
pascal@24476
|
474 scasw ; di += 2
|
pascal@24476
|
475 scasw ; point to next entry
|
pascal@24476
|
476
|
pascal@24476
|
477 RelocateEXE:
|
pascal@24942
|
478 dec word [bx+06h] ; reloc items, 32768 max (128KB table)
|
pascal@24942
|
479 jns ReloCycle
|
pascal@24476
|
480 ; PSP don't have a valid drive identifier
|
pascal@24476
|
481 les si, [bx+0Eh]
|
pascal@24476
|
482 add si, bp
|
pascal@24476
|
483 mov ss, si ; ss for EXE
|
pascal@24476
|
484 mov sp, es ; sp for EXE
|
pascal@24476
|
485
|
pascal@24476
|
486 lea si, [bp-10h] ; ds and es both point to the segment
|
pascal@24476
|
487 push si ; containing the PSP structure
|
pascal@24476
|
488
|
pascal@24476
|
489 add bp, [bx+16h] ; cs for EXE
|
pascal@24942
|
490 mov di, [bx+14h] ; ip for EXE
|
pascal@24476
|
491 Run:
|
pascal@24476
|
492 pop ds
|
pascal@24476
|
493 push bp
|
pascal@24942
|
494 push di
|
pascal@24476
|
495 push ds
|
pascal@24476
|
496 pop es
|
pascal@24942
|
497 mov [80h], ax ; clear cmdline
|
pascal@24942
|
498 dec ax ; both FCB in the PSP don't have a valid drive identifier
|
pascal@24476
|
499
|
pascal@24476
|
500 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
501 ;; Set the magic numbers so the program knows that it ;;
|
pascal@24476
|
502 ;; has been loaded by this bootsector and not by MS-DOS ;;
|
pascal@24476
|
503 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
504 mov si, 16381 ; prime number 2**14-3
|
pascal@24476
|
505 mov di, 32749 ; prime number 2**15-19
|
pascal@24476
|
506 mov bp, 65521 ; prime number 2**16-15
|
pascal@24476
|
507
|
pascal@24476
|
508 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
509 ;; All done, transfer control to the program now ;;
|
pascal@24476
|
510 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
511 retf
|
pascal@24476
|
512
|
pascal@25458
|
513 ;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@25458
|
514 ;; Error Messaging Code ;;
|
pascal@25458
|
515 ;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@25458
|
516
|
pascal@25458
|
517 Error:
|
pascal@25458
|
518 pop si
|
pascal@25458
|
519
|
pascal@25458
|
520 PutStr:
|
pascal@25458
|
521 mov ah, 0Eh
|
pascal@25458
|
522 mov bl, 7
|
pascal@25458
|
523 lodsb
|
pascal@25458
|
524 int 10h
|
pascal@25458
|
525 cmp al, "."
|
pascal@25458
|
526 jne PutStr
|
pascal@25564
|
527 %if WaitForKey != 0
|
pascal@25458
|
528 cbw
|
pascal@25458
|
529 int 16h ; wait for a key...
|
pascal@25458
|
530 int 19h ; bootstrap
|
pascal@25564
|
531 %endif
|
pascal@25458
|
532 Stop:
|
pascal@25458
|
533 hlt
|
pascal@25458
|
534 jmp short Stop
|
pascal@25458
|
535
|
pascal@25458
|
536 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@25458
|
537 ;; Read sectors using BIOS Int 13h ;;
|
pascal@25458
|
538 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@25458
|
539 ;; Input: DX:AX = LBA relative to FAT ;;
|
pascal@25458
|
540 ;; BX = 0 ;;
|
pascal@25458
|
541 ;; DI = sector count ;;
|
pascal@25458
|
542 ;; ES:BX -> buffer address ;;
|
pascal@25458
|
543 ;; Output: ES:BX -> next address ;;
|
pascal@25458
|
544 ;; BX = 0 ;;
|
pascal@25458
|
545 ;; CX = 0 ;;
|
pascal@25458
|
546 ;; DI = 0 ;;
|
pascal@25458
|
547 ;; DL = drive number ;;
|
pascal@25564
|
548 ;; 0:BP = next LBA from FAT ;;
|
pascal@25458
|
549 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@25458
|
550
|
pascal@25458
|
551 ReadDISectors:
|
pascal@25458
|
552 mov bp, di
|
pascal@24476
|
553 add bp, ax ; adjust LBA for cluster data
|
pascal@24476
|
554
|
pascal@25458
|
555 mov cx, di ; no cluster size limit
|
pascal@24476
|
556
|
pascal@24476
|
557 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@25458
|
558 ;; Read sectors using BIOS Int 13h ;;
|
pascal@24476
|
559 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
560 ;; Input: DX:AX = LBA relative to FAT ;;
|
pascal@24476
|
561 ;; BX = 0 ;;
|
pascal@24476
|
562 ;; CX = sector count ;;
|
pascal@24476
|
563 ;; DI = file sectors ;;
|
pascal@24476
|
564 ;; ES:BX -> buffer address ;;
|
pascal@24476
|
565 ;; Output: ES:BX -> next address ;;
|
pascal@24476
|
566 ;; BX = 0 ;;
|
pascal@24476
|
567 ;; CX or DI = 0 ;;
|
pascal@24476
|
568 ;; DL = drive number ;;
|
pascal@25564
|
569 ;; Keep: BP, SI ;;
|
pascal@24476
|
570 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
571
|
pascal@25458
|
572 ReadSectors:
|
pascal@24476
|
573 add ax, [bx(bpbHiddenSectors)]
|
pascal@24476
|
574 adc dx, [bx(bpbHiddenSectors)+2]
|
pascal@24476
|
575 add ax, [bx(bpbReservedSectors)]
|
pascal@24476
|
576
|
pascal@24476
|
577 push si
|
pascal@24476
|
578 ReadSectorNext:
|
pascal@24476
|
579 adc dx, bx
|
pascal@24476
|
580 push di
|
pascal@24476
|
581 push cx
|
pascal@24476
|
582
|
pascal@25450
|
583 %if LBAsupport != 0
|
pascal@24476
|
584 push bx
|
pascal@24476
|
585 push bx
|
pascal@25450
|
586 %endif
|
pascal@24476
|
587 push dx ; 32-bit LBA: up to 2TB
|
pascal@24476
|
588 push ax
|
pascal@24476
|
589 push es
|
pascal@25450
|
590 %if ReadRetry != 0 || LBAsupport != 0
|
pascal@25450
|
591 mov di, 16 ; packet size byte = 16, reserved byte = 0
|
pascal@25450
|
592 %endif
|
pascal@25450
|
593 %if LBAsupport != 0
|
pascal@24476
|
594 push bx
|
pascal@24476
|
595 inc bx ; sector count word = 1
|
pascal@24476
|
596 push bx
|
pascal@24476
|
597 dec bx
|
pascal@24476
|
598 push di
|
pascal@25450
|
599 %endif
|
pascal@24476
|
600
|
pascal@24476
|
601 xchg ax, cx ; save low LBA
|
pascal@24476
|
602 xchg ax, dx ; get high LBA
|
pascal@25452
|
603 cwd ; clear dx (LBA offset <1TB)
|
pascal@25450
|
604 idiv word [bx(bpbSectorsPerTrack)] ; up to 8GB disks
|
pascal@24476
|
605
|
pascal@25564
|
606 %if CHSsanityCheck != 0
|
pascal@25564
|
607 inc ax
|
pascal@25564
|
608 cmp ax, [bx(bpbHeadsPerCylinder)]
|
pascal@25564
|
609 ja CHSoverflow
|
pascal@25564
|
610 dec ax
|
pascal@25564
|
611 %endif
|
pascal@24476
|
612 xchg ax, cx ; restore low LBA, save high LBA / SPT
|
pascal@25450
|
613 idiv word [bx(bpbSectorsPerTrack)]
|
pascal@24476
|
614 ; ax = LBA / SPT
|
pascal@24476
|
615 ; dx = LBA % SPT = sector - 1
|
pascal@24476
|
616 inc dx
|
pascal@24476
|
617
|
pascal@24476
|
618 xchg cx, dx ; restore high LBA / SPT, save sector no.
|
pascal@25564
|
619 idiv word [bx(bpbHeadsPerCylinder)] ; may overflow if SectorsPerTrack * HeadsPerCylinder < 256 or disk > 8GB
|
pascal@24476
|
620 ; ax = (LBA / SPT) / HPC = cylinder
|
pascal@24476
|
621 ; dx = (LBA / SPT) % HPC = head
|
pascal@25458
|
622
|
pascal@25458
|
623 xchg ch, al ; clear al
|
pascal@24476
|
624 ; ch = LSB 0...7 of cylinder no.
|
pascal@25458
|
625 shr ax, 1
|
pascal@25458
|
626 shr ax, 1
|
pascal@24476
|
627 or cl, al
|
pascal@24476
|
628 ; cl = MSB 8...9 of cylinder no. + sector no.
|
pascal@24476
|
629 mov dh, dl
|
pascal@24476
|
630 ; dh = head no.
|
pascal@24476
|
631
|
pascal@25564
|
632 %if CHSsanityCheck != 0
|
pascal@25564
|
633 %if LBAsupport != 0
|
pascal@25564
|
634 or ah, [si+8+3] ; 8GB max, last cylinder 1023
|
pascal@25564
|
635 %else
|
pascal@25564
|
636 or ah, [si+2+3] ; 8GB max, last cylinder 1023
|
pascal@25564
|
637 %endif
|
pascal@25564
|
638 %endif
|
pascal@25564
|
639 CHSoverflow:
|
pascal@25450
|
640 mov dl, [bx(DriveNumber)]
|
pascal@24476
|
641 ; dl = drive no.
|
pascal@25450
|
642 mov si, sp
|
pascal@25564
|
643 %if CHSsanityCheck != 0
|
pascal@25564
|
644 %if ReadRetry != 0 || LBAsupport != 0
|
pascal@25564
|
645 pushf
|
pascal@25564
|
646 %endif
|
pascal@25564
|
647 %endif
|
pascal@25564
|
648
|
pascal@25564
|
649 ReadSectorRetry:
|
pascal@25450
|
650 %if LBAsupport != 0
|
pascal@24476
|
651 mov ah, 42h ; ah = 42h = extended read function no.
|
pascal@24476
|
652 int 13h ; extended read sectors (DL, DS:SI)
|
pascal@24476
|
653 jnc ReadSectorNextSegment
|
pascal@25450
|
654 %endif
|
pascal@25564
|
655 %if CHSsanityCheck != 0
|
pascal@25564
|
656 %if ReadRetry != 0 || LBAsupport != 0
|
pascal@25564
|
657 popf
|
pascal@25564
|
658 pushf
|
pascal@25564
|
659 %endif
|
pascal@25564
|
660 jne SkipCHS
|
pascal@25564
|
661 %endif
|
pascal@24476
|
662
|
pascal@24476
|
663 mov ax, 201h ; al = sector count = 1
|
pascal@24476
|
664 ; ah = 2 = read function no.
|
pascal@24476
|
665 int 13h ; read sectors (AL, CX, DX, ES:BX)
|
pascal@24476
|
666
|
pascal@24476
|
667 jnc ReadSectorNextSegment
|
pascal@25564
|
668 SkipCHS:
|
pascal@25450
|
669 %if ReadRetry != 0
|
pascal@24476
|
670 cbw ; ah = 0 = reset function
|
pascal@24476
|
671 int 13h ; reset drive (DL)
|
pascal@24476
|
672
|
pascal@24476
|
673 dec di
|
pascal@25457
|
674 jnz ReadSectorRetry ; up to 15 extra attempt
|
pascal@25450
|
675 %endif
|
pascal@24476
|
676
|
pascal@25564
|
677 ReadError:
|
pascal@24476
|
678 call Error
|
pascal@24476
|
679 db "Read error."
|
pascal@24476
|
680
|
pascal@24476
|
681 ReadSectorNextSegment:
|
pascal@25564
|
682 %if CHSsanityCheck != 0 && (ReadRetry != 0 || LBAsupport != 0)
|
pascal@25564
|
683 popf
|
pascal@25564
|
684 %endif
|
pascal@25564
|
685
|
pascal@25564
|
686 %macro adjust_es 2
|
pascal@25564
|
687 %if SectorOf512Bytes != 0
|
pascal@25564
|
688 add word %1, byte 32 ; adjust segment for next sector
|
pascal@25564
|
689 %else
|
pascal@25564
|
690 %if %2 != 0
|
pascal@25564
|
691 mov al, %2
|
pascal@25564
|
692 %endif
|
pascal@25564
|
693 mul byte [bx(bpbBytesPerSector)+1] ; = (bpbBytesPerSector/256)*16
|
pascal@25564
|
694 add %1, ax ; adjust segment for next sector
|
pascal@25564
|
695 %endif
|
pascal@25564
|
696 %endmacro
|
pascal@24476
|
697
|
pascal@25450
|
698 %if LBAsupport != 0
|
pascal@24476
|
699 pop ax ; al = 16
|
pascal@25564
|
700 adjust_es [si+6], 0
|
pascal@24476
|
701 pop cx ; sector count = 1
|
pascal@24476
|
702 pop bx
|
pascal@25450
|
703 %else
|
pascal@25564
|
704 adjust_es [si], 16
|
pascal@25450
|
705 %endif
|
pascal@24476
|
706 pop es ; es:0 updated
|
pascal@24476
|
707 pop ax
|
pascal@24476
|
708 pop dx
|
pascal@25450
|
709 %if LBAsupport != 0
|
pascal@24476
|
710 pop di
|
pascal@24476
|
711 pop di
|
pascal@24476
|
712 add ax, cx ; adjust LBA for next sector
|
pascal@25450
|
713 %else
|
pascal@25450
|
714 add ax, 1 ; adjust LBA for next sector
|
pascal@25450
|
715 %endif
|
pascal@24476
|
716
|
pascal@24476
|
717 pop cx ; cluster sectors to read
|
pascal@24476
|
718 pop di ; file sectors to read
|
pascal@24476
|
719 dec di ; keep C
|
pascal@25457
|
720 loopne ReadSectorNext ; until cluster sector count or file sector count
|
pascal@24476
|
721 pop si
|
pascal@24942
|
722 mov ax, bx ; clear ax
|
pascal@25450
|
723 mov dx, [bx(DriveNumber)] ; pass the BIOS boot drive to Run or Error
|
pascal@24476
|
724
|
pascal@24476
|
725 ret
|
pascal@24476
|
726
|
pascal@24942
|
727 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24942
|
728 ;; Fill free space with zeroes ;;
|
pascal@24942
|
729 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24942
|
730
|
pascal@25458
|
731 times (512-13-($-$$)) db 0
|
pascal@24476
|
732
|
pascal@24476
|
733 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
734 ;; Name of the file to load and run ;;
|
pascal@24476
|
735 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
736
|
pascal@25463
|
737 NameLength equ 11
|
pascal@25463
|
738 ProgramName times NameLength db 0 ; name and extension
|
pascal@24476
|
739
|
pascal@24476
|
740 ;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
741 ;; End of the sector ID ;;
|
pascal@24476
|
742 ;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
743
|
pascal@24476
|
744 ClusterList dw 0AA55h ; BIOS checks for this ID
|