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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@25569
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14 ;; - FAT12 and/or 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
|
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
|
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
|
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@25572
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26 ;; - cpu 8088 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
|
33 ;; ;;
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pascal@25572
|
34 ;; - Partition must fit in the first 8GB of the disk for CHS reads. ;;
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pascal@25569
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35 ;; (or 2TB for LBA reads). ;;
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pascal@25564
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36 ;; ;;
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pascal@25564
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37 ;; ;;
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pascal@24476
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38 ;; Known Bugs: ;;
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pascal@24476
|
39 ;; ~~~~~~~~~~~ ;;
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pascal@24476
|
40 ;; - All bugs are fixed as far as I know. The boot sector has been tested ;;
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pascal@24476
|
41 ;; on the following types of diskettes (FAT12): ;;
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pascal@24476
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42 ;; - 360KB 5"25 ;;
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pascal@24476
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43 ;; - 1.2MB 5"25 ;;
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pascal@24476
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44 ;; - 1.44MB 3"5 ;;
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pascal@24476
|
45 ;; on my HDD (FAT16). ;;
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pascal@24476
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46 ;; ;;
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pascal@24476
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47 ;; ;;
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pascal@24476
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48 ;; Memory Layout: ;;
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pascal@24476
|
49 ;; ~~~~~~~~~~~~~~ ;;
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pascal@24476
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50 ;; The diagram below shows the typical memory layout. The actual location ;;
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pascal@24476
|
51 ;; 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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52 ;; reserves memory for its Extended BIOS Data Area just below A0000H and ;;
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pascal@24476
|
53 ;; reports less than 640 KB of RAM via its Int 12H function. ;;
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pascal@24476
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54 ;; ;;
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pascal@24476
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55 ;; physical address ;;
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pascal@24476
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56 ;; +------------------------+ 00000H ;;
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pascal@24476
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57 ;; | Interrupt Vector Table | ;;
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pascal@24476
|
58 ;; +------------------------+ 00400H ;;
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pascal@24476
|
59 ;; | BIOS Data Area | ;;
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pascal@24476
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60 ;; +------------------------+ 00500H ;;
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pascal@24476
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61 ;; | PrtScr Status / Unused | ;;
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pascal@24476
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62 ;; +------------------------+ 00600H ;;
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pascal@24476
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63 ;; | Loaded Image | ;;
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pascal@24476
|
64 ;; +------------------------+ nnnnnH ;;
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pascal@24476
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65 ;; | Available Memory | ;;
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pascal@24476
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66 ;; +------------------------+ A0000H - 512 - 3KB ;;
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pascal@24476
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67 ;; | Boot Sector | ;;
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pascal@24476
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68 ;; +------------------------+ A0000H - 3KB ;;
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pascal@24476
|
69 ;; | 3KB Boot Stack | ;;
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pascal@24476
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70 ;; +------------------------+ A0000H ;;
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pascal@24476
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71 ;; | Video RAM | ;;
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pascal@24476
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72 ;; ;;
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pascal@24476
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73 ;; ;;
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pascal@24476
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74 ;; Boot Image Startup (register values): ;;
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pascal@24476
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75 ;; ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ;;
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pascal@24945
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76 ;; ax = 0ffffh (both FCB in the PSP don't have a valid drive identifier), ;;
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pascal@25454
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77 ;; bx = 0, dl = BIOS boot drive number (e.g. 0, 80H) ;;
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pascal@24476
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78 ;; cs:ip = program entry point ;;
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pascal@24476
|
79 ;; ss:sp = program stack (don't confuse with boot sector's stack) ;;
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pascal@24476
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80 ;; COM program defaults: cs = ds = es = ss = 50h, sp = 0, ip = 100h ;;
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pascal@24476
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81 ;; EXE program defaults: ds = es = EXE data - 10h (fake MS-DOS psp), ;;
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pascal@24476
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82 ;; cs:ip and ss:sp depends on EXE header ;;
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pascal@24476
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83 ;; Magic numbers: ;;
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pascal@24476
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84 ;; si = 16381 (prime number 2**14-3) ;;
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pascal@24476
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85 ;; di = 32749 (prime number 2**15-19) ;;
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pascal@24476
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86 ;; bp = 65521 (prime number 2**16-15) ;;
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pascal@24476
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87 ;; The magic numbers let the program know whether it has been loaded by ;;
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pascal@24476
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88 ;; this boot sector or by MS-DOS, which may be handy for universal, bare- ;;
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pascal@24476
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89 ;; metal and MS-DOS programs. ;;
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pascal@24945
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90 ;; The command line contains no arguments. ;;
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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
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pascal@24476
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94 %define bx(label) bx+label-boot
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pascal@25450
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95 %define si(label) si+label-boot
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pascal@25458
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96 NullEntryCheck equ 1 ; +2 bytes
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pascal@25569
|
97 ReadRetry equ 1 ; +9/+13 bytes
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pascal@25569
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98 LBAsupport equ 1 ; +18 bytes
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pascal@25578
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99 CHSsanityCheck equ 1 ; +9/+13 bytes
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pascal@25569
|
100 GeometryCheck equ 1 ; +20 bytes
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pascal@25564
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101 CheckAttrib equ 0 ; +6 bytes
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pascal@25564
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102 WaitForKey equ 0 ; +5 bytes
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pascal@25550
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103 SectorOf512Bytes equ 0 ; -4/-6 bytes
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pascal@25564
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104 Always2FATs equ 0 ; -1 bytes
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pascal@25698
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105 AnyWhere equ 1 ; +4 bytes
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pascal@24476
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106
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pascal@24476
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107 [BITS 16]
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pascal@24476
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108 [CPU 8086]
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pascal@24476
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109
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pascal@24476
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110 ImageLoadSeg equ 60h
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pascal@24476
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111 StackSize equ 3072 ; Stack + cluster list
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pascal@24476
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112
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pascal@24476
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113 [SECTION .text]
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pascal@24476
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114 [ORG 0]
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pascal@24476
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115
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pascal@24476
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116 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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117 ;; Boot sector starts here ;;
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pascal@24476
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118 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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119
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pascal@24476
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120 boot:
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pascal@25450
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121 DriveNumber:
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pascal@24476
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122 jmp short start ; MS-DOS/Windows checks for this jump
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pascal@24476
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123 nop
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pascal@24476
|
124 bsOemName DB "BootProg" ; 0x03
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pascal@24476
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125
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pascal@24476
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126 ;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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127 ;; BPB starts here ;;
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pascal@24476
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128 ;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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129
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pascal@25564
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130 bpbBytesPerSector DW 0 ; 0x0B 512, 1024, 2048 or 4096
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pascal@25564
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131 bpbSectorsPerCluster DB 0 ; 0x0D 1, 2, 4, 8, 16, 32 or 64
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pascal@25564
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132 bpbReservedSectors DW 0 ; 0x0E 1
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pascal@25564
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133 bpbNumberOfFATs DB 0 ; 0x10 2
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pascal@24479
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134 bpbRootEntries DW 0 ; 0x11
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pascal@24479
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135 bpbTotalSectors DW 0 ; 0x13
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pascal@24479
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136 bpbMedia DB 0 ; 0x15
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pascal@24479
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137 bpbSectorsPerFAT DW 0 ; 0x16
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pascal@24479
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138 bpbSectorsPerTrack DW 0 ; 0x18
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pascal@24479
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139 bpbHeadsPerCylinder DW 0 ; 0x1A
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pascal@24479
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140 bpbHiddenSectors DD 0 ; 0x1C
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pascal@24479
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141 bpbTotalSectorsBig DD 0 ; 0x20
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pascal@24476
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142
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pascal@24476
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143 ;;;;;;;;;;;;;;;;;;;
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pascal@24476
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144 ;; BPB ends here ;;
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pascal@24476
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145 ;;;;;;;;;;;;;;;;;;;
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pascal@24476
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146
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pascal@24479
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147 bsDriveNumber DB 0 ; 0x24
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pascal@24479
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148 bsUnused DB 0 ; 0x25
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pascal@25564
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149 bsExtBootSignature DB 0 ; 0x26 29
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pascal@24479
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150 bsSerialNumber DD 0 ; 0x27
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pascal@25458
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151 bsVolumeLabel times 11 DB " " ; 0x2B "NO NAME "
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pascal@25458
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152 bsFileSystem times 8 DB " " ; 0x36 "FAT12 " or "FAT16 "
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pascal@24476
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153
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pascal@24476
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154 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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155 ;; Boot sector code starts here ;;
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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 start:
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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 ;; How much RAM is there? ;;
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pascal@24476
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162 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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163
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pascal@24476
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164 int 12h ; get conventional memory size (in KBs)
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pascal@25698
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165 %if AnyWhere
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pascal@25698
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166 call here
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pascal@25698
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167 here:
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pascal@25698
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168 pop si
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pascal@25698
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169 sub si, here - boot
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pascal@25698
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170 push cs
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pascal@25698
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171 pop ds
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pascal@25698
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172 %endif
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pascal@24476
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173 mov cx, 106h
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pascal@24476
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174 shl ax, cl ; and convert it to 16-byte paragraphs
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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 ;; Reserve memory for the boot sector and its stack ;;
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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 sub ax, (512+StackSize) /16 ; reserve bytes for the code and the stack
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pascal@24476
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181 mov es, ax ; cs:0 = ds:0 = ss:0 -> top - 512 - StackSize
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pascal@24476
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182 mov ss, ax
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pascal@24476
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183 mov sp, 512+StackSize ; bytes 0-511 are reserved for the boot code
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pascal@24476
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184
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pascal@24476
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185 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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186 ;; Copy ourselves to top of memory ;;
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pascal@24476
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187 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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188
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pascal@25698
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189 xor di, di
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pascal@25698
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190 %if AnyWhere == 0
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pascal@24476
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191 mov si, 7C00h
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pascal@24476
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192 mov ds, di
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pascal@25698
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193 %endif
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pascal@25450
|
194 push es
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pascal@25450
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195 mov [si(DriveNumber)], dx ; store BIOS boot drive number
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pascal@25698
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196 cld
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pascal@24476
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197 rep movsw ; move 512 bytes (+ 12)
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pascal@24476
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198
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pascal@24476
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199 ;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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200 ;; Jump to the copy ;;
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pascal@24476
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201 ;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
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202
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pascal@24476
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203 mov cl, byte main
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pascal@24476
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204 push cx
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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@24476
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207 main:
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pascal@24476
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208 %if ImageLoadSeg != main-boot
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pascal@24476
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209 %if ImageLoadSeg >= 100h
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pascal@24476
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210 mov cx, ImageLoadSeg
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pascal@24476
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211 %else
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pascal@24476
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212 mov cl, ImageLoadSeg
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pascal@24476
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213 %endif
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pascal@24476
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214 %endif
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pascal@24476
|
215 push cx
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pascal@24476
|
216
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pascal@24476
|
217 ;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
|
218 ;; Get drive parameters ;;
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pascal@24476
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219 ;; Update heads count ;;
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pascal@24476
|
220 ;; for current BIOS ;;
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pascal@24476
|
221 ;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
|
222
|
pascal@25450
|
223 %if GeometryCheck != 0
|
pascal@25564
|
224 %if ((main-boot) & 3Fh) != 0
|
pascal@25569
|
225 xor cx, cx
|
pascal@25564
|
226 %endif
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pascal@25564
|
227 mov ah, 8 ; update AX,BL,CX,DX,DI, and ES registers
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pascal@24476
|
228 int 13h ; may destroy SI,BP, and DS registers
|
pascal@25450
|
229 %endif
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pascal@24476
|
230 push cs
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pascal@24476
|
231 pop ds
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pascal@24476
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232 xor bx, bx
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pascal@24476
|
233
|
pascal@25450
|
234 %if GeometryCheck != 0
|
pascal@24479
|
235 and cx, byte 3Fh
|
pascal@25564
|
236 je BadParams ; verify updated and validity
|
pascal@25564
|
237 mov [bx(bpbSectorsPerTrack)], cx
|
pascal@25564
|
238 mov cl, dh
|
pascal@25564
|
239 inc cx
|
pascal@25564
|
240 mov [bx(bpbHeadsPerCylinder)], cx
|
pascal@24476
|
241 BadParams:
|
pascal@25450
|
242 %endif
|
pascal@24476
|
243
|
pascal@24476
|
244 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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pascal@24476
|
245 ;; Load FAT (FAT12: 6KB max, FAT16: 128KB max) ;;
|
pascal@24476
|
246 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
247
|
pascal@24476
|
248 pop es ; ImageLoadSeg
|
pascal@24476
|
249 push es
|
pascal@24476
|
250
|
pascal@24476
|
251 mul bx ; dx:ax = 0 = LBA (LBA are relative to FAT)
|
pascal@25458
|
252 mov di, word [bx(bpbSectorsPerFAT)]
|
pascal@24476
|
253
|
pascal@25458
|
254 call ReadDISectors ; read fat; clear ax, cx, di; bp = SectorsPerFAT
|
pascal@24476
|
255
|
pascal@24476
|
256 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
257 ;; load the root directory in ;;
|
pascal@24476
|
258 ;; its entirety (16KB max) ;;
|
pascal@24476
|
259 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
260
|
pascal@25458
|
261 %if SectorOf512Bytes != 0
|
pascal@25458
|
262 mov di, word [bx(bpbRootEntries)]
|
pascal@25458
|
263 mov cl, 4
|
pascal@25458
|
264 shr di, cl ; di = root directory size in sectors
|
pascal@25458
|
265 %else
|
pascal@24942
|
266 mov al, 32
|
pascal@24476
|
267
|
pascal@24476
|
268 mul word [bx(bpbRootEntries)]
|
pascal@24476
|
269 div word [bx(bpbBytesPerSector)]
|
pascal@25458
|
270 xchg ax, di ; di = root directory size in sectors, clear ah
|
pascal@25458
|
271 %endif
|
pascal@24476
|
272
|
pascal@25564
|
273 %if Always2FATs != 0
|
pascal@25564
|
274 mov al, 2
|
pascal@25564
|
275 %else
|
pascal@24476
|
276 mov al, [bpbNumberOfFATs]
|
pascal@25564
|
277 %endif
|
pascal@25458
|
278 mul bp ; [bx(bpbSectorsPerFAT)], set by ReadDISectors
|
pascal@24476
|
279
|
pascal@25457
|
280 push es ; read root directory
|
pascal@25458
|
281 call ReadDISectors ; clear ax, cx, di; bp = first data sector
|
pascal@24476
|
282 pop es
|
pascal@24476
|
283
|
pascal@24476
|
284 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
285 ;; Look for the COM/EXE file to load and run ;;
|
pascal@24476
|
286 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
287
|
pascal@24476
|
288 ; es:di -> root entries array
|
pascal@24476
|
289
|
pascal@24476
|
290 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
291 ;; Looks for the file/dir ProgramName ;;
|
pascal@24476
|
292 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
293 ;; Input: ES:DI -> root directory array ;;
|
pascal@24476
|
294 ;; Output: SI = cluster number ;;
|
pascal@24476
|
295 ;; AX = file sector count ;;
|
pascal@24476
|
296 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
297
|
pascal@24476
|
298 FindNameCycle:
|
pascal@24476
|
299 push di
|
pascal@25454
|
300 mov cl, NameLength
|
pascal@24476
|
301 mov si, ProgramName ; ds:si -> program name
|
pascal@24476
|
302 repe cmpsb
|
pascal@25467
|
303 %if CheckAttrib != 0
|
pascal@25467
|
304 VolumeLabel equ 8
|
pascal@25467
|
305 SubDirectory equ 10h
|
pascal@25467
|
306 jnz SkipFindName
|
pascal@25467
|
307 test byte [es:di], VolumeLabel+SubDirectory
|
pascal@25467
|
308 SkipFindName:
|
pascal@25467
|
309 %endif
|
pascal@24476
|
310 pop di
|
pascal@24476
|
311 je FindNameFound
|
pascal@25450
|
312 %if NullEntryCheck != 0
|
pascal@25564
|
313 scasb ; Z == NC
|
pascal@25458
|
314 cmc
|
pascal@25458
|
315 lea di, [di+31]
|
pascal@25458
|
316 dec word [bx(bpbRootEntries)]
|
pascal@25458
|
317 ja FindNameCycle ; next root entry
|
pascal@25450
|
318 %else
|
pascal@25450
|
319 add di, byte 32
|
pascal@24476
|
320 dec word [bx(bpbRootEntries)]
|
pascal@24476
|
321 jnz FindNameCycle ; next root entry
|
pascal@25458
|
322 %endif
|
pascal@24476
|
323
|
pascal@24476
|
324 FindNameFailed:
|
pascal@24476
|
325 call Error
|
pascal@24476
|
326 db "File not found."
|
pascal@24476
|
327
|
pascal@24476
|
328 FindNameFound:
|
pascal@24476
|
329 push si
|
pascal@24476
|
330 mov si, [es:di+1Ah] ; si = cluster no.
|
pascal@24476
|
331 les ax, [es:di+1Ch] ; file size
|
pascal@24476
|
332 mov dx, es
|
pascal@24476
|
333 div word [bx(bpbBytesPerSector)]
|
pascal@24476
|
334 cmp bx, dx ; sector aligned ?
|
pascal@24476
|
335 adc ax, bx ; file last sector
|
pascal@24476
|
336 pop di ; di = ClusterList
|
pascal@24476
|
337
|
pascal@24476
|
338 pop es ; ImageLoadSeg
|
pascal@24476
|
339 push ax
|
pascal@24476
|
340
|
pascal@24476
|
341 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
342 ;; build cluster list ;;
|
pascal@24476
|
343 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
344 ;; Input: ES:0 -> FAT ;;
|
pascal@24476
|
345 ;; SI = first cluster ;;
|
pascal@24476
|
346 ;; DI = cluster list :;
|
pascal@24476
|
347 ;; CH = 0 ;;
|
pascal@24476
|
348 ;; Output: SI = cluster list ;;
|
pascal@24476
|
349 ;; CH = 0 ;;
|
pascal@24476
|
350 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
351
|
pascal@25458
|
352 FAT12 equ 1
|
pascal@25458
|
353 FAT16 equ 1
|
pascal@25550
|
354 TINYFAT16 equ 1 ; < 4072 clusters fat16 support
|
pascal@25453
|
355 push di ; up to 2 * 635K / BytesPerCluster = 2540 bytes
|
pascal@25572
|
356 %if FAT12 != 1 && FAT16 != 1
|
pascal@25572
|
357 %error "FAT12 and/or FAT16 must be set"
|
pascal@25572
|
358 %endif
|
pascal@25450
|
359 %if FAT12 == 1
|
pascal@25454
|
360 mov cl, 12
|
pascal@25564
|
361 %else
|
pascal@25564
|
362 nop
|
pascal@25564
|
363 nop
|
pascal@25450
|
364 %endif
|
pascal@24476
|
365 ClusterLoop:
|
pascal@24476
|
366 mov [di], si
|
pascal@25450
|
367 add si, si ; si = cluster * 2
|
pascal@25450
|
368 %if FAT16 == 1
|
pascal@24476
|
369 mov ax, es ; ax = FAT segment = ImageLoadSeg
|
pascal@25094
|
370 jnc First64k
|
pascal@24476
|
371 mov ah, (1000h+ImageLoadSeg)>>8 ; adjust segment for 2nd part of FAT16
|
pascal@25094
|
372 First64k:
|
pascal@25453
|
373 %if FAT12 == 1
|
pascal@25457
|
374 mov dx, 0FFF6h
|
pascal@25454
|
375 %if TINYFAT16 == 1
|
pascal@25550
|
376 test [bx(bsFileSystem+4)], cl ; FAT12 or FAT16 ? clear C (bit 2)
|
pascal@25458
|
377 jne ReadClusterFat16
|
pascal@25454
|
378 %else
|
pascal@25454
|
379 cmp [bx(bpbSectorsPerFAT)], cx ; 1..12 = FAT12, 16..256 = FAT16
|
pascal@25458
|
380 ja ReadClusterFat16
|
pascal@25454
|
381 %endif
|
pascal@24942
|
382 mov dh, 0Fh
|
pascal@25453
|
383 %endif
|
pascal@25450
|
384 %endif
|
pascal@25450
|
385 %if FAT12 == 1
|
pascal@25087
|
386 add si, [di]
|
pascal@24476
|
387 shr si, 1 ; si = cluster * 3 / 2
|
pascal@25564
|
388 %else
|
pascal@25564
|
389 nop
|
pascal@25564
|
390 nop
|
pascal@25450
|
391 %endif
|
pascal@25450
|
392 %if FAT16 == 1
|
pascal@24942
|
393 ReadClusterFat16:
|
pascal@25094
|
394 push ds
|
pascal@25087
|
395 mov ds, ax
|
pascal@24476
|
396 lodsw ; ax = next cluster
|
pascal@25094
|
397 pop ds
|
pascal@25450
|
398 %else
|
pascal@25453
|
399 es lodsw
|
pascal@25450
|
400 %endif
|
pascal@25450
|
401 %if FAT12 == 1
|
pascal@24476
|
402 jnc ReadClusterEven
|
pascal@25454
|
403 rol ax, cl
|
pascal@24476
|
404 ReadClusterEven:
|
pascal@25094
|
405 scasw ; di += 2
|
pascal@25454
|
406 %if FAT16 == 1
|
pascal@24942
|
407 and ah, dh ; mask cluster value
|
pascal@24942
|
408 cmp ax, dx
|
pascal@25454
|
409 %else
|
pascal@25453
|
410 and ah, 0Fh ; mask cluster value
|
pascal@25457
|
411 cmp ax, 0FF6h
|
pascal@25454
|
412 %endif
|
pascal@25454
|
413 %else
|
pascal@25454
|
414 scasw ; di += 2
|
pascal@25457
|
415 cmp ax, 0FFF6h
|
pascal@25453
|
416 %endif
|
pascal@24476
|
417 xchg ax, si
|
pascal@24476
|
418 jc ClusterLoop
|
pascal@24476
|
419 pop si
|
pascal@24476
|
420 pop di ; file size in sectors
|
pascal@24476
|
421
|
pascal@24476
|
422 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
423 ;; Load the entire file ;;
|
pascal@24476
|
424 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
425 ;; Input: ES:0 -> buffer ;;
|
pascal@24476
|
426 ;; SI = cluster list ;;
|
pascal@24476
|
427 ;; DI = file sectors ;;
|
pascal@24476
|
428 ;; CH = 0 ;;
|
pascal@24945
|
429 ;; BP = 1st data sec ;;
|
pascal@24476
|
430 ;; Output: BP:0 -> buffer ;;
|
pascal@24476
|
431 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
432
|
pascal@24476
|
433 push es
|
pascal@24476
|
434
|
pascal@24476
|
435 ReadClusters:
|
pascal@24476
|
436 lodsw
|
pascal@24476
|
437 dec ax
|
pascal@24476
|
438 dec ax
|
pascal@24476
|
439
|
pascal@25454
|
440 mov cl, [bx(bpbSectorsPerCluster)] ; 1..128
|
pascal@24476
|
441 mul cx ; cx = sector count (ch = 0)
|
pascal@24476
|
442
|
pascal@24476
|
443 add ax, bp ; LBA for cluster data
|
pascal@24476
|
444 adc dx, bx ; dx:ax = LBA
|
pascal@24476
|
445
|
pascal@25458
|
446 call ReadSectors ; clear ax, restore dx
|
pascal@24476
|
447
|
pascal@25458
|
448 jne ReadClusters ; until end of file
|
pascal@24476
|
449
|
pascal@24476
|
450 pop bp ; ImageLoadSeg
|
pascal@24476
|
451
|
pascal@24476
|
452 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
453 ;; Type detection, .COM or .EXE? ;;
|
pascal@24476
|
454 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
455
|
pascal@24476
|
456 mov ds, bp ; bp=ds=seg the file is loaded to
|
pascal@24476
|
457
|
pascal@24476
|
458 add bp, [bx+08h] ; bp = image base
|
pascal@24476
|
459 mov di, [bx+18h] ; di = reloc table pointer
|
pascal@24476
|
460
|
pascal@24476
|
461 cmp word [bx], 5A4Dh ; "MZ" signature?
|
pascal@24476
|
462 je RelocateEXE ; yes, it's an EXE program
|
pascal@24476
|
463
|
pascal@24476
|
464 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
465 ;; Setup and run a .COM program ;;
|
pascal@24476
|
466 ;; Set CS=DS=ES=SS SP=0 IP=100h ;;
|
pascal@25454
|
467 ;; AX=0ffffh BX=0 DX=drive and ;;
|
pascal@25454
|
468 ;; cmdline=void ;;
|
pascal@24476
|
469 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
470
|
pascal@24942
|
471 mov di, 100h ; ip
|
pascal@24476
|
472 mov bp, ImageLoadSeg-10h ; "org 100h" stuff :)
|
pascal@24476
|
473 mov ss, bp
|
pascal@24476
|
474 xor sp, sp
|
pascal@24476
|
475 push bp ; cs, ds and es
|
pascal@24476
|
476 jmp short Run
|
pascal@24476
|
477
|
pascal@24476
|
478 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
479 ;; Relocate, setup and run a .EXE program ;;
|
pascal@24476
|
480 ;; Set CS:IP, SS:SP, DS, ES and AX according ;;
|
pascal@24476
|
481 ;; to wiki.osdev.org/MZ#Initial_Program_State ;;
|
pascal@25454
|
482 ;; AX=0ffffh BX=0 DX=drive cmdline=void ;;
|
pascal@24476
|
483 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
484
|
pascal@24476
|
485 ReloCycle:
|
pascal@24476
|
486 add [di+2], bp ; item seg (abs)
|
pascal@24476
|
487 les si, [di] ; si = item ofs, es = item seg
|
pascal@24476
|
488 add [es:si], bp ; fixup
|
pascal@24476
|
489 scasw ; di += 2
|
pascal@24476
|
490 scasw ; point to next entry
|
pascal@24476
|
491
|
pascal@24476
|
492 RelocateEXE:
|
pascal@24942
|
493 dec word [bx+06h] ; reloc items, 32768 max (128KB table)
|
pascal@24942
|
494 jns ReloCycle
|
pascal@24476
|
495 ; PSP don't have a valid drive identifier
|
pascal@24476
|
496 les si, [bx+0Eh]
|
pascal@24476
|
497 add si, bp
|
pascal@24476
|
498 mov ss, si ; ss for EXE
|
pascal@24476
|
499 mov sp, es ; sp for EXE
|
pascal@24476
|
500
|
pascal@24476
|
501 lea si, [bp-10h] ; ds and es both point to the segment
|
pascal@24476
|
502 push si ; containing the PSP structure
|
pascal@24476
|
503
|
pascal@24476
|
504 add bp, [bx+16h] ; cs for EXE
|
pascal@24942
|
505 mov di, [bx+14h] ; ip for EXE
|
pascal@24476
|
506 Run:
|
pascal@24476
|
507 pop ds
|
pascal@24476
|
508 push bp
|
pascal@24942
|
509 push di
|
pascal@24476
|
510 push ds
|
pascal@24476
|
511 pop es
|
pascal@24942
|
512 mov [80h], ax ; clear cmdline
|
pascal@24942
|
513 dec ax ; both FCB in the PSP don't have a valid drive identifier
|
pascal@24476
|
514
|
pascal@24476
|
515 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
516 ;; Set the magic numbers so the program knows that it ;;
|
pascal@24476
|
517 ;; has been loaded by this bootsector and not by MS-DOS ;;
|
pascal@24476
|
518 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
519 mov si, 16381 ; prime number 2**14-3
|
pascal@24476
|
520 mov di, 32749 ; prime number 2**15-19
|
pascal@24476
|
521 mov bp, 65521 ; prime number 2**16-15
|
pascal@24476
|
522
|
pascal@24476
|
523 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
524 ;; All done, transfer control to the program now ;;
|
pascal@24476
|
525 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
526 retf
|
pascal@24476
|
527
|
pascal@25458
|
528 ;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@25458
|
529 ;; Error Messaging Code ;;
|
pascal@25458
|
530 ;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@25458
|
531
|
pascal@25458
|
532 Error:
|
pascal@25458
|
533 pop si
|
pascal@25458
|
534
|
pascal@25458
|
535 PutStr:
|
pascal@25458
|
536 mov ah, 0Eh
|
pascal@25458
|
537 mov bl, 7
|
pascal@25458
|
538 lodsb
|
pascal@25458
|
539 int 10h
|
pascal@25458
|
540 cmp al, "."
|
pascal@25458
|
541 jne PutStr
|
pascal@25564
|
542 %if WaitForKey != 0
|
pascal@25458
|
543 cbw
|
pascal@25458
|
544 int 16h ; wait for a key...
|
pascal@25458
|
545 int 19h ; bootstrap
|
pascal@25564
|
546 %endif
|
pascal@25458
|
547 Stop:
|
pascal@25458
|
548 hlt
|
pascal@25458
|
549 jmp short Stop
|
pascal@25458
|
550
|
pascal@25458
|
551 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@25458
|
552 ;; Read sectors using BIOS Int 13h ;;
|
pascal@25458
|
553 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@25458
|
554 ;; Input: DX:AX = LBA relative to FAT ;;
|
pascal@25458
|
555 ;; BX = 0 ;;
|
pascal@25458
|
556 ;; DI = sector count ;;
|
pascal@25458
|
557 ;; ES:BX -> buffer address ;;
|
pascal@25458
|
558 ;; Output: ES:BX -> next address ;;
|
pascal@25458
|
559 ;; BX = 0 ;;
|
pascal@25458
|
560 ;; CX = 0 ;;
|
pascal@25458
|
561 ;; DI = 0 ;;
|
pascal@25458
|
562 ;; DL = drive number ;;
|
pascal@25564
|
563 ;; 0:BP = next LBA from FAT ;;
|
pascal@25458
|
564 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@25458
|
565
|
pascal@25458
|
566 ReadDISectors:
|
pascal@25458
|
567 mov bp, di
|
pascal@24476
|
568 add bp, ax ; adjust LBA for cluster data
|
pascal@24476
|
569
|
pascal@25458
|
570 mov cx, di ; no cluster size limit
|
pascal@24476
|
571
|
pascal@24476
|
572 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@25458
|
573 ;; Read sectors using BIOS Int 13h ;;
|
pascal@24476
|
574 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
575 ;; Input: DX:AX = LBA relative to FAT ;;
|
pascal@24476
|
576 ;; BX = 0 ;;
|
pascal@24476
|
577 ;; CX = sector count ;;
|
pascal@24476
|
578 ;; DI = file sectors ;;
|
pascal@24476
|
579 ;; ES:BX -> buffer address ;;
|
pascal@24476
|
580 ;; Output: ES:BX -> next address ;;
|
pascal@24476
|
581 ;; BX = 0 ;;
|
pascal@24476
|
582 ;; CX or DI = 0 ;;
|
pascal@24476
|
583 ;; DL = drive number ;;
|
pascal@25564
|
584 ;; Keep: BP, SI ;;
|
pascal@24476
|
585 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
586
|
pascal@25458
|
587 ReadSectors:
|
pascal@24476
|
588 add ax, [bx(bpbHiddenSectors)]
|
pascal@24476
|
589 adc dx, [bx(bpbHiddenSectors)+2]
|
pascal@24476
|
590 add ax, [bx(bpbReservedSectors)]
|
pascal@24476
|
591
|
pascal@24476
|
592 push si
|
pascal@24476
|
593 ReadSectorNext:
|
pascal@24476
|
594 adc dx, bx
|
pascal@24476
|
595 push di
|
pascal@24476
|
596 push cx
|
pascal@24476
|
597
|
pascal@25450
|
598 %if LBAsupport != 0
|
pascal@24476
|
599 push bx
|
pascal@24476
|
600 push bx
|
pascal@25450
|
601 %endif
|
pascal@24476
|
602 push dx ; 32-bit LBA: up to 2TB
|
pascal@24476
|
603 push ax
|
pascal@24476
|
604 push es
|
pascal@25450
|
605 %if ReadRetry != 0 || LBAsupport != 0
|
pascal@25450
|
606 mov di, 16 ; packet size byte = 16, reserved byte = 0
|
pascal@25450
|
607 %endif
|
pascal@25450
|
608 %if LBAsupport != 0
|
pascal@24476
|
609 push bx
|
pascal@24476
|
610 inc bx ; sector count word = 1
|
pascal@24476
|
611 push bx
|
pascal@24476
|
612 dec bx
|
pascal@24476
|
613 push di
|
pascal@25450
|
614 %endif
|
pascal@24476
|
615
|
pascal@24476
|
616 xchg ax, cx ; save low LBA
|
pascal@24476
|
617 xchg ax, dx ; get high LBA
|
pascal@25452
|
618 cwd ; clear dx (LBA offset <1TB)
|
pascal@25450
|
619 idiv word [bx(bpbSectorsPerTrack)] ; up to 8GB disks
|
pascal@24476
|
620
|
pascal@25569
|
621 %if CHSsanityCheck != 0
|
pascal@25564
|
622 cmp ax, [bx(bpbHeadsPerCylinder)]
|
pascal@25578
|
623 jns CHSoverflow
|
pascal@25569
|
624 %endif
|
pascal@24476
|
625 xchg ax, cx ; restore low LBA, save high LBA / SPT
|
pascal@25450
|
626 idiv word [bx(bpbSectorsPerTrack)]
|
pascal@24476
|
627 ; ax = LBA / SPT
|
pascal@24476
|
628 ; dx = LBA % SPT = sector - 1
|
pascal@24476
|
629 inc dx
|
pascal@24476
|
630
|
pascal@24476
|
631 xchg cx, dx ; restore high LBA / SPT, save sector no.
|
pascal@25564
|
632 idiv word [bx(bpbHeadsPerCylinder)] ; may overflow if SectorsPerTrack * HeadsPerCylinder < 256 or disk > 8GB
|
pascal@24476
|
633 ; ax = (LBA / SPT) / HPC = cylinder
|
pascal@24476
|
634 ; dx = (LBA / SPT) % HPC = head
|
pascal@25458
|
635
|
pascal@25578
|
636 xchg ch, al ; clear al, save cylinder no.
|
pascal@24476
|
637 ; ch = LSB 0...7 of cylinder no.
|
pascal@25458
|
638 shr ax, 1
|
pascal@25458
|
639 shr ax, 1
|
pascal@24476
|
640 or cl, al
|
pascal@24476
|
641 ; cl = MSB 8...9 of cylinder no. + sector no.
|
pascal@24476
|
642 mov dh, dl
|
pascal@24476
|
643 ; dh = head no.
|
pascal@24476
|
644
|
pascal@25564
|
645 %if CHSsanityCheck != 0
|
pascal@25578
|
646 dec ah ; set S if cylinder < 1024 (8GB max)
|
pascal@25572
|
647 CHSoverflow:
|
pascal@25564
|
648 %endif
|
pascal@25572
|
649 mov si, sp
|
pascal@25569
|
650 %if CHSsanityCheck != 0 && (ReadRetry != 0 || LBAsupport != 0)
|
pascal@25564
|
651 pushf
|
pascal@25564
|
652 %endif
|
pascal@25564
|
653
|
pascal@25564
|
654 ReadSectorRetry:
|
pascal@25569
|
655 mov dl, [bx(DriveNumber)]
|
pascal@25569
|
656 ; dl = drive no.
|
pascal@25450
|
657 %if LBAsupport != 0
|
pascal@24476
|
658 mov ah, 42h ; ah = 42h = extended read function no.
|
pascal@24476
|
659 int 13h ; extended read sectors (DL, DS:SI)
|
pascal@24476
|
660 jnc ReadSectorNextSegment
|
pascal@25450
|
661 %endif
|
pascal@25572
|
662 mov ax, 201h ; al = sector count = 1
|
pascal@25572
|
663 ; ah = 2 = read function no.
|
pascal@25564
|
664 %if CHSsanityCheck != 0
|
pascal@25564
|
665 %if ReadRetry != 0 || LBAsupport != 0
|
pascal@25564
|
666 popf
|
pascal@25564
|
667 pushf
|
pascal@25564
|
668 %endif
|
pascal@25578
|
669 jns SkipCHS
|
pascal@25564
|
670 %endif
|
pascal@24476
|
671 int 13h ; read sectors (AL, CX, DX, ES:BX)
|
pascal@24476
|
672 jnc ReadSectorNextSegment
|
pascal@25564
|
673 SkipCHS:
|
pascal@25450
|
674 %if ReadRetry != 0
|
pascal@24476
|
675 cbw ; ah = 0 = reset function
|
pascal@24476
|
676 int 13h ; reset drive (DL)
|
pascal@24476
|
677 dec di
|
pascal@25457
|
678 jnz ReadSectorRetry ; up to 15 extra attempt
|
pascal@25450
|
679 %endif
|
pascal@24476
|
680
|
pascal@25564
|
681 ReadError:
|
pascal@24476
|
682 call Error
|
pascal@24476
|
683 db "Read error."
|
pascal@24476
|
684
|
pascal@24476
|
685 ReadSectorNextSegment:
|
pascal@25564
|
686 %if CHSsanityCheck != 0 && (ReadRetry != 0 || LBAsupport != 0)
|
pascal@25564
|
687 popf
|
pascal@25564
|
688 %endif
|
pascal@25564
|
689
|
pascal@25564
|
690 %macro adjust_es 2
|
pascal@25564
|
691 %if SectorOf512Bytes != 0
|
pascal@25564
|
692 add word %1, byte 32 ; adjust segment for next sector
|
pascal@25564
|
693 %else
|
pascal@25564
|
694 %if %2 != 0
|
pascal@25564
|
695 mov al, %2
|
pascal@25564
|
696 %endif
|
pascal@25564
|
697 mul byte [bx(bpbBytesPerSector)+1] ; = (bpbBytesPerSector/256)*16
|
pascal@25564
|
698 add %1, ax ; adjust segment for next sector
|
pascal@25564
|
699 %endif
|
pascal@25564
|
700 %endmacro
|
pascal@24476
|
701
|
pascal@25450
|
702 %if LBAsupport != 0
|
pascal@24476
|
703 pop ax ; al = 16
|
pascal@25564
|
704 adjust_es [si+6], 0
|
pascal@24476
|
705 pop cx ; sector count = 1
|
pascal@24476
|
706 pop bx
|
pascal@25450
|
707 %else
|
pascal@25564
|
708 adjust_es [si], 16
|
pascal@25450
|
709 %endif
|
pascal@24476
|
710 pop es ; es:0 updated
|
pascal@24476
|
711 pop ax
|
pascal@24476
|
712 pop dx
|
pascal@25450
|
713 %if LBAsupport != 0
|
pascal@24476
|
714 pop di
|
pascal@24476
|
715 pop di
|
pascal@24476
|
716 add ax, cx ; adjust LBA for next sector
|
pascal@25450
|
717 %else
|
pascal@25450
|
718 add ax, 1 ; adjust LBA for next sector
|
pascal@25450
|
719 %endif
|
pascal@24476
|
720
|
pascal@24476
|
721 pop cx ; cluster sectors to read
|
pascal@24476
|
722 pop di ; file sectors to read
|
pascal@24476
|
723 dec di ; keep C
|
pascal@25457
|
724 loopne ReadSectorNext ; until cluster sector count or file sector count
|
pascal@24476
|
725 pop si
|
pascal@24942
|
726 mov ax, bx ; clear ax
|
pascal@25450
|
727 mov dx, [bx(DriveNumber)] ; pass the BIOS boot drive to Run or Error
|
pascal@24476
|
728
|
pascal@24476
|
729 ret
|
pascal@24476
|
730
|
pascal@24942
|
731 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24942
|
732 ;; Fill free space with zeroes ;;
|
pascal@24942
|
733 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24942
|
734
|
pascal@25458
|
735 times (512-13-($-$$)) db 0
|
pascal@24476
|
736
|
pascal@24476
|
737 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
738 ;; Name of the file to load and run ;;
|
pascal@24476
|
739 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
740
|
pascal@25463
|
741 NameLength equ 11
|
pascal@25463
|
742 ProgramName times NameLength db 0 ; name and extension
|
pascal@24476
|
743
|
pascal@24476
|
744 ;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
745 ;; End of the sector ID ;;
|
pascal@24476
|
746 ;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
747
|
pascal@24476
|
748 ClusterList dw 0AA55h ; BIOS checks for this ID
|