freeldr/bootsect/win2k.asm

   1 segment .text
   2
   3 bits 16
   4
   5 start:
   6         jmp short main
   7         nop
   8
   9 OEMName                         db 'FreeLDR!'
  10 BytesPerSector          dw 512
  11 SectsPerCluster         db 1
  12 ReservedSectors         dw 1
  13 NumberOfFats            db 2
  14 MaxRootEntries          dw 0                    ;512 - Always zero for FAT32 volumes
  15 TotalSectors            dw 0                    ;2880 - Always zero for FAT32 volumes
  16 MediaDescriptor         db 0f8h
  17 SectorsPerFat           dw 0                    ;9 - Always zero for FAT32 volumes
  18 SectorsPerTrack         dw 18
  19 NumberOfHeads           dw 2
  20 HiddenSectors           dd 0
  21 TotalSectorsBig         dd 0
  22 ; FAT32 Inserted Info
  23 SectorsPerFatBig        dd      0
  24 ExtendedFlags           dw      0
  25 FSVersion                       dw      0
  26 RootDirStartCluster     dd      0
  27 FSInfoSector            dw      0
  28 BackupBootSector        dw      6
  29 Reserved1                       times 12 db 0
  30 ; End FAT32 Inserted Info
  31 BootDrive                       db 0
  32 Reserved                        db 0
  33 ExtendSig                       db 29h
  34 SerialNumber            dd 00000000h
  35 VolumeLabel                     db 'FreeLoader!'
  36 FileSystem                      db 'FAT12   '
  37
  38 main:
  39 00007C5A  33C9              xor         cx,cx
  40 00007C5C  8ED1              mov         ss,cx
  41 00007C5E  BCF47B            mov         sp,0x7bf4
  42 00007C61  8EC1              mov         es,cx
  43 00007C63  8ED9              mov         ds,cx
  44 00007C65  BD007C            mov         bp,0x7c00
  45 00007C68  884E02            mov         [bp+0x2],cl
  46 00007C6B  8A5640            mov         dl,[bp+BootDrive]
  47 00007C6E  B408              mov         ah,0x8
  48 00007C70  CD13              int         0x13                    ; Int 13, func 8 - Get Drive Parameters
  49 00007C72  7305              jnc         0x7c79                  ; If no error jmp
  50
  51 00007C74  B9FFFF            mov         cx,0xffff
  52 00007C77  8AF1              mov         dh,cl
  53
  54 00007C79  660FB6C6          movzx       eax,dh
  55 00007C7D  40                inc         ax
  56 00007C7E  660FB6D1          movzx       edx,cl
  57 00007C82  80E23F            and         dl,0x3f
  58 00007C85  F7E2              mul         dx
  59 00007C87  86CD              xchg        cl,ch
  60 00007C89  C0ED06            shr         ch,0x6
  61 00007C8C  41                inc         cx
  62 00007C8D  660FB7C9          movzx       ecx,cx
  63 00007C91  66F7E1            mul         ecx
  64 00007C94  668946F8          mov         [bp-0x8],eax
  65 00007C98  837E1600          cmp         word [bp+TotalSectors],byte +0x0
  66 00007C9C  7538              jnz         print_ntldr_error_message
  67
  68 00007C9E  837E2A00          cmp         word [bp+FSVersion],byte +0x0
  69 00007CA2  7732              ja          print_ntldr_error_message
  70
  71 00007CA4  668B461C          mov         eax,[bp+0x1c]
  72 00007CA8  6683C00C          add         eax,byte +0xc
  73 00007CAC  BB0080            mov         bx,0x8000
  74 00007CAF  B90100            mov         cx,0x1
  75 00007CB2  E82B00            call        read_sectors
  76 00007CB5  E94803            jmp         0x8000
  77
  78 print_disk_error_message:
  79 00007CB8  A0FA7D            mov         al,[DISK_ERR_offset_from_0x7d00]
  80 putchars:
  81 00007CBB  B47D              mov         ah,0x7d
  82 00007CBD  8BF0              mov         si,ax
  83 get_another_char:
  84 00007CBF  AC                lodsb
  85 00007CC0  84C0              test        al,al
  86 00007CC2  7417              jz          reboot
  87 00007CC4  3CFF              cmp         al,0xff
  88 00007CC6  7409              jz          print_reboot_message
  89 00007CC8  B40E              mov         ah,0xe
  90 00007CCA  BB0700            mov         bx,0x7
  91 00007CCD  CD10              int         0x10
  92 00007CCF  EBEE              jmp         short get_another_char
  93 print_reboot_message:
  94 00007CD1  A0FB7D            mov         al,[RESTART_ERR_offset_from_0x7d00]
  95 00007CD4  EBE5              jmp         short putchars
  96 print_ntldr_error_message:
  97 00007CD6  A0F97D            mov         al,[NTLDR_ERR_offset_from_0x7d00]
  98 00007CD9  EBE0              jmp         short putchars
  99 reboot:
 100 00007CDB  98                cbw
 101 00007CDC  CD16              int         0x16
 102 00007CDE  CD19              int         0x19
 103
 104 read_sectors:
 105 00007CE0  6660              pushad
 106 00007CE2  663B46F8          cmp         eax,[bp-0x8]
 107 00007CE6  0F824A00          jc          near 0x7d34
 108 00007CEA  666A00            o32         push byte +0x0
 109 00007CED  6650              push        eax
 110 00007CEF  06                push        es
 111 00007CF0  53                push        bx
 112 00007CF1  666810000100      push        dword 0x10010
 113 00007CF7  807E0200          cmp         byte [bp+0x2],0x0
 114 00007CFB  0F852000          jnz         near 0x7d1f
 115 00007CFF  B441              mov         ah,0x41
 116 00007D01  BBAA55            mov         bx,0x55aa
 117 00007D04  8A5640            mov         dl,[bp+BootDrive]
 118 00007D07  CD13              int         0x13
 119 00007D09  0F821C00          jc          near 0x7d29
 120 00007D0D  81FB55AA          cmp         bx,0xaa55
 121 00007D11  0F851400          jnz         near 0x7d29
 122 00007D15  F6C101            test        cl,0x1
 123 00007D18  0F840D00          jz          near 0x7d29
 124 00007D1C  FE4602            inc         byte [bp+0x2]
 125 00007D1F  B442              mov         ah,0x42
 126 00007D21  8A5640            mov         dl,[bp+BootDrive]
 127 00007D24  8BF4              mov         si,sp
 128 00007D26  CD13              int         0x13
 129 00007D28  B0F9              mov         al,0xf9
 130 00007D2A  6658              pop         eax
 131 00007D2C  6658              pop         eax
 132 00007D2E  6658              pop         eax
 133 00007D30  6658              pop         eax
 134 00007D32  EB2A              jmp         short 0x7d5e
 135 00007D34  6633D2            xor         edx,edx
 136 00007D37  660FB74E18        movzx       ecx,word [bp+SectorsPerTrack]
 137 00007D3C  66F7F1            div         ecx
 138 00007D3F  FEC2              inc         dl
 139 00007D41  8ACA              mov         cl,dl
 140 00007D43  668BD0            mov         edx,eax
 141 00007D46  66C1EA10          shr         edx,0x10
 142 00007D4A  F7761A            div         word [bp+NumberOfHeads]
 143 00007D4D  86D6              xchg        dl,dh
 144 00007D4F  8A5640            mov         dl,[bp+BootDrive]
 145 00007D52  8AE8              mov         ch,al
 146 00007D54  C0E406            shl         ah,0x6
 147 00007D57  0ACC              or          cl,ah
 148 00007D59  B80102            mov         ax,0x201
 149 00007D5C  CD13              int         0x13
 150 00007D5E  6661              popad
 151 00007D60  0F8254FF          jc          near print_disk_error_message
 152 00007D64  81C30002          add         bx,0x200
 153 00007D68  6640              inc         eax
 154 00007D6A  49                dec         cx
 155 00007D6B  0F8571FF          jnz         near read_sectors
 156 00007D6F  C3                ret
 157
 158 NTLDR           db 'NTLDR      '
 159
 160 filler          times 49        db 0
 161
 162 NTLDR_ERR       db 0dh,0ah,'NTLDR is missing',0ffh
 163 DISK_ERR        db 0dh,0ah,'Disk error',0ffh
 164 RESTART_ERR     db 0dh,0ah,'Press any key to restart',0dh,0ah
 165
 166 more_filler     times 16        db 0
 167
 168 NTLDR_offset_from_0x7d00                                                db 0
 169 NTLDR_ERR_offset_from_0x7d00                                    db 0ach
 170 DISK_ERR_offset_from_0x7d00                                             db 0bfh
 171 RESTART_ERR_offset_from_0x7d00                                  db 0cch
 172
 173                                                 dw 0
 174                                                 dw 0aa55h