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| ; Copyright (c) 2008-2009, diamond |
| ; All rights reserved. |
| ; |
| ; Redistribution and use in source and binary forms, with or without |
| ; modification, are permitted provided that the following conditions are met: |
| ; * Redistributions of source code must retain the above copyright |
| ; notice, this list of conditions and the following disclaimer. |
| ; * Redistributions in binary form must reproduce the above copyright |
| ; notice, this list of conditions and the following disclaimer in the |
| ; documentation and/or other materials provided with the distribution. |
| ; * Neither the name of the <organization> nor the |
| ; names of its contributors may be used to endorse or promote products |
| ; derived from this software without specific prior written permission. |
| ; |
| ; THIS SOFTWARE IS PROVIDED BY Alexey Teplov aka <Lrz> ''AS IS'' AND ANY |
| ; EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED |
| ; WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE |
| ; DISCLAIMED. IN NO EVENT SHALL <copyright holder> BE LIABLE FOR ANY |
| ; DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES |
| ; (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; |
| ; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND |
| ; ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| ; (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS |
| ; SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| ;***************************************************************************** |
| |
| use_lba = 0 |
| org 0x7C00 |
| jmp start |
| nop |
| ; FAT parameters, BPB |
| ; they must be changed at install, replaced with real values |
| rb 8 ; BS_OEMName, ignored |
| dw 200h ; BPB_BytsPerSec |
| BPB_SecsPerClus db ? |
| BPB_RsvdSecCnt dw ? |
| BPB_NumFATs db ? |
| BPB_RootEntCnt dw ? |
| dw ? ; BPB_TotSec16 |
| db ? ; BPB_Media |
| dw ? ; BPB_FATSz16 = 0 for FAT32 |
| BPB_SecPerTrk dw ? |
| BPB_NumHeads dw ? |
| BPB_HiddSec dd ? |
| dd ? ; BPB_TotSec32 |
| BPB_FATSz32 dd ? |
| BPB_ExtFlags dw ? |
| dw ? ; BPB_FSVer |
| BPB_RootClus dd ? |
| dw ? ; BPB_FSInfo |
| BPB_BkBootSec dw ? |
| rb 12 ; BPB_Reserved |
| BS_DrvNum db ? |
| db ? ; BS_Reserved1 |
| db ? ; BS_BootSig |
| dd ? ; BS_VolID |
| rb 11 ; BS_VolLab |
| rb 8 ; |
| |
| curseg dw 0x8000 |
| |
| start: |
| xor ax, ax |
| mov ss, ax |
| mov sp, 0x7C00 |
| mov ds, ax |
| mov bp, sp |
| cld |
| sti |
| push dx ; byte [bp-2] = boot drive |
| if use_lba |
| mov ah, 41h |
| mov bx, 55AAh |
| int 13h |
| mov si, aNoLBA |
| jc err |
| cmp bx, 0AA55h |
| jnz err |
| test cl, 1 |
| jz err |
| else |
| mov ah, 8 |
| int 13h |
| jc @f |
| movzx ax, dh |
| inc ax |
| mov [bp+BPB_NumHeads-0x7C00], ax |
| and cx, 3Fh |
| mov [bp+BPB_SecPerTrk-0x7C00], cx |
| @@: |
| end if |
| ; get FAT parameters |
| xor bx, bx |
| movzx eax, [bp+BPB_NumFATs-0x7C00] |
| mul [bp+BPB_FATSz32-0x7C00] |
| movzx ecx, [bp+BPB_RsvdSecCnt-0x7C00] |
| push ecx ; FAT start = dword [bp-6] |
| add eax, ecx |
| push eax ; data start = dword [bp-10] |
| ;push dword -1 ; dword [bp-14] = current sector for FAT cache |
| db 66h |
| push -1 ; dword [bp-14] = current sector for FAT cache |
| mov eax, [bp+BPB_RootClus-0x7C00] |
| mov si, main_loader |
| call lookup_in_dir |
| jnc kordldr_ok |
| noloader: |
| mov si, aLoaderNotFound |
| err: |
| call out_string |
| mov si, aPressAnyKey |
| call out_string |
| xor ax, ax |
| int 16h |
| int 18h |
| jmp $ |
| kordldr_ok: |
| mov eax, [es:di+20-2] ; hiword(eax) = hiword(cluster) |
| mov ax, [es:di+26] ; loword(eax) = loword(cluster) |
| mov es, bx ; es = 0 |
| mov bx, 0x7E00 |
| push bx ; save return address: bx = 7E00 |
| ; fall through - 'ret' in read_cluster will return to 7E00 |
| |
| read_cluster: |
| ; ss:bp = 0:7C00 |
| ; es:bx = pointer to data |
| ; eax = cluster |
| sub eax, 2 |
| movzx ecx, [bp+BPB_SecsPerClus-0x7C00] |
| mul ecx |
| |
| read_sectors2: |
| ; same as read_sectors32, but eax is relative to start of data |
| add eax, [bp-10] |
| read_sectors32: |
| ; ss:bp = 0:7C00 |
| ; es:bx = pointer to data |
| ; eax = first sector |
| ; cx = number of sectors |
| ; some high words of 32-bit registers are destroyed! |
| pusha |
| add eax, [bp+BPB_HiddSec-0x7C00] |
| if use_lba |
| push ds |
| do_read_sectors: |
| push ax |
| push cx |
| cmp cx, 0x7F |
| jbe @f |
| mov cx, 0x7F |
| @@: |
| ; create disk address packet on the stack |
| ; dq starting LBA |
| push 0 |
| push 0 |
| push eax |
| ; dd buffer |
| push es |
| push bx |
| ; dw number of blocks to transfer (no more than 0x7F) |
| push cx |
| ; dw packet size in bytes |
| push 10h |
| ; issue BIOS call |
| push ss |
| pop ds |
| mov si, sp |
| mov dl, [bp-2] |
| mov ah, 42h |
| int 13h |
| mov si, aReadError |
| jc err |
| ; restore stack |
| add sp, 10h |
| ; increase current sector & buffer; decrease number of sectors |
| movzx esi, cx |
| mov ax, es |
| shl cx, 5 |
| add ax, cx |
| mov es, ax |
| pop cx |
| pop ax |
| add eax, esi |
| sub cx, si |
| jnz do_read_sectors |
| pop ds |
| popa |
| ret |
| else |
| do_read_sectors: |
| pusha |
| pop edi ; loword(edi) = di, hiword(edi) = si |
| push bx |
| |
| ; eax / (SectorsPerTrack) -> eax, remainder bx |
| movzx esi, [bp+BPB_SecPerTrk-0x7C00] |
| xor edx, edx |
| div esi |
| mov bx, dx ; bx=sector-1 |
| |
| ; eax -> dx:ax |
| push eax |
| pop ax |
| pop dx |
| ; (dword in dx:ax) / (NumHeads) -> (word in ax), remainder dx |
| div [bp+BPB_NumHeads-0x7C00] |
| |
| ; number of sectors: read no more than to end of track |
| sub si, bx |
| cmp cx, si |
| jbe @f |
| mov cx, si |
| @@: |
| |
| inc bx |
| ; now ax=track, dl=head, dh=0, cl=number of sectors, ch=0, bl=sector; convert to int13 format |
| movzx edi, cx |
| mov dh, dl |
| mov dl, [bp-2] |
| shl ah, 6 |
| mov ch, al |
| mov al, cl |
| mov cl, bl |
| or cl, ah |
| pop bx |
| mov si, 3 |
| mov ah, 2 |
| @@: |
| push ax |
| int 13h |
| jnc @f |
| xor ax, ax |
| int 13h ; reset drive |
| pop ax |
| dec si |
| jnz @b |
| mov si, aReadError |
| jmp err |
| @@: |
| pop ax |
| mov ax, es |
| mov cx, di |
| shl cx, 5 |
| add ax, cx |
| mov es, ax |
| push edi |
| popa |
| add eax, edi |
| sub cx, di |
| jnz do_read_sectors |
| popa |
| ret |
| end if |
| |
| lookup_in_dir: |
| ; in: ds:si -> 11-bytes FAT name |
| ; in: eax = cluster |
| ; in: bx = 0 |
| ; out: if found: CF=0, es:di -> directory entry |
| ; out: if not found: CF=1 |
| ; push 0x8000 |
| ; pop es |
| ; read current cluster: first cluster goes to 8000:0000, others - to 8200:0000 |
| mov es, [bp-7C00h + curseg] |
| push es |
| push eax |
| call read_cluster |
| mov ax, es |
| cmp ah, 82h |
| jb @f |
| mov ax, 8200h |
| @@: |
| mov [bp-7C00h + curseg], ax |
| pop eax |
| pop es |
| ; scan for filename |
| shl cx, 4 |
| xor di, di |
| sloop: |
| cmp byte [es:di], bl |
| jz snotfound |
| test byte [es:di+11], 8 ; volume label? |
| jnz scont ; ignore volume labels |
| pusha |
| mov cx, 11 |
| repz cmpsb |
| popa |
| jz sdone |
| scont: |
| add di, 0x20 |
| loop sloop |
| ; next cluster |
| push 0x6000 |
| pop es |
| push es ax |
| shr eax, 7 |
| cmp eax, [bp-14] |
| mov [bp-14], eax |
| jz @f |
| add eax, [bp-6] |
| mov cx, 1 |
| call read_sectors32 |
| @@: |
| pop di es |
| and di, 0x7F |
| shl di, 2 |
| and byte [es:di+3], 0x0F |
| mov eax, [es:di] |
| ;and eax, 0x0FFFFFFF |
| cmp eax, 0x0FFFFFF7 |
| jb lookup_in_dir |
| snotfound: |
| stc |
| sdone: |
| ret |
| |
| out_string: |
| ; in: ds:si -> ASCIIZ string |
| lodsb |
| test al, al |
| jz sdone |
| mov ah, 0Eh |
| mov bx, 7 |
| int 10h |
| jmp out_string |
| |
| aReadError db 'Read error',0 |
| if use_lba |
| aNoLBA db 'The drive does not support LBA!',0 |
| end if |
| aLoaderNotFound db 'Loader not found',0 |
| aPressAnyKey db 13,10,'Press any key...',13,10,0 |
| main_loader db 'KORDLDR F32' |
| |
| db 56h |
| ; just to make file 512 bytes long :) |
| db 'd' xor 'i' xor 'a' xor 'm' xor 'o' xor 'n' xor 'd' |
| |
| ; bootsector signature |
| dw 0xAA55 |
| |
| ; display offsets of all procedures used by kordldr.f12.asm |
| macro show [procedure] |
| { |
| bits = 16 |
| display `procedure,' = ' |
| repeat bits/4 |
| d = '0' + procedure shr (bits - %*4) and 0Fh |
| if d > '9' |
| d = d + 'A'-'9'-1 |
| end if |
| display d |
| end repeat |
| display 13,10 |
| } |
| |
| show read_sectors32, read_sectors2, err, noloader |