kolibrios/kernel/branches/Kolibri-acpi/sec_loader/trunk/boot/fat1x/bootsect.asm

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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
; note: they can be changed at install, replaced with real values
; these settings are for most typical 1.44M floppies
db 'KOLIBRI ' ; BS_OEMName, ignored
dw 200h ; BPB_BytsPerSec
BPB_SecsPerClus db 1
BPB_RsvdSecCnt dw 1
BPB_NumFATs db 2
BPB_RootEntCnt dw 0xE0
dw 2880 ; BPB_TotSec16
db 0xF0 ; BPB_Media
BPB_FATSz16 dw 9
BPB_SecPerTrk dw 18
BPB_NumHeads dw 2
BPB_HiddSec dd 0
dd 0 ; BPB_TotSec32
BS_DrvNum db 0
db 0 ; BS_Reserved1
db ')' ; BS_BootSig
dd 12344321h ; BS_VolID
filename:
db 'KORD.OS ' ; BS_VolLab
db 'FAT12 ' ; BS_FilSysType
; Used memory map:
; 8000:0000 - current directory
; 9000:0000 - root directory data [cached]
start:
xor ax, ax
mov ss, ax
mov sp, 0x7C00
mov ds, ax
mov bp, sp
cld
sti
mov [bp+BS_DrvNum-0x7C00], dl
if use_lba
mov ah, 41h
mov bx, 55AAh
int 13h
mov si, aNoLBA
jc err_
cmp bx, 0AA55h
jnz err_
test cx, 1
jz err_
else
mov ah, 8
int 13h
jc @f ; on error, assume that BPB geometry is valid
mov al, dh
mov ah, 0
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
mov al, [bp+BPB_NumFATs-0x7C00]
mov ah, 0
mul [bp+BPB_FATSz16-0x7C00]
add ax, [bp+BPB_RsvdSecCnt-0x7C00]
adc dx, bx
push dx
push ax ; root directory start = dword [bp-4]
mov cx, [bp+BPB_RootEntCnt-0x7C00]
add cx, 0xF
rcr cx, 1
shr cx, 3 ; cx = size of root directory in sectors
add ax, cx
adc dx, bx
push dx
push ax ; data start = dword [bp-8]
; load start of root directory (no more than 0x2000 bytes = 0x10 sectors)
cmp cx, 0x10
jb @f
mov cx, 0x10
@@:
mov ax, [bp-4]
mov dx, [bp-2]
push 0x9000
pop es
call read_sectors
add word [bp-4], cx ; dword [bp-4] = start of non-cached root data
adc word [bp-2], bx
; load kordldr.f12
mov si, main_loader
call lookup_in_root_dir
jc noloader
test byte [es:di+11], 10h ; directory?
jz 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 ax, [es:di+26] ; get file cluster
mov bx, 0x7E00
xor cx, cx
mov es, cx
sub ax, 2
jc noloader
push bx ; save return address: bx = 7E00
mov cl, [bp+BPB_SecsPerClus-0x7C00]
mul cx
; fall through - 'ret' in read_sectors will return to 7E00
read_sectors2:
; same as read_sectors, but dx:ax is relative to start of data
add ax, [bp-8]
adc dx, [bp-6]
read_sectors:
; ss:bp = 0:7C00
; es:bx = pointer to data
; dx:ax = first sector
; cx = number of sectors
pusha
add ax, word [bp+BPB_HiddSec-0x7C00]
adc dx, word [bp+BPB_HiddSec+2-0x7C00]
if use_lba
push ds
do_read_sectors:
push ax
push cx
push dx
cmp cx, 0x7F
jbe @f
mov cx, 0x7F
@@:
; create disk address packet on the stack
; dq starting LBA
push 0
push 0
push dx
push ax
; 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+BS_DrvNum-0x7C00]
mov ah, 42h
int 13h
mov si, aReadError
jc err_
; restore stack
add sp, 10h
; increase current sector & buffer; decrease number of sectors
mov si, cx
mov ax, es
shl cx, 5
add ax, cx
mov es, ax
pop dx
pop cx
pop ax
add ax, si
adc dx, 0
sub cx, si
jnz do_read_sectors
pop ds
popa
ret
else
do_read_sectors:
pusha
pop di
push bx
; (dword in dx:ax) / (SectorsPerTrack) -> (dword in dx:ax), remainder bx
mov si, ax
xchg ax, dx
xor dx, dx
div [bp+BPB_SecPerTrk-0x7C00]
push ax
mov ax, si
div [bp+BPB_SecPerTrk-0x7C00]
mov bx, dx ; bx=sector-1
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
push bx
sub bx, [bp+BPB_SecPerTrk-0x7C00]
neg bx
cmp cx, bx
jbe @f
mov cx, bx
@@:
pop bx
inc bx
; now ax=track, dl=head, dh=0, cl=number of sectors, ch=0, bl=sector; convert to int13 format
mov di, cx
mov dh, dl
mov dl, [bp+BS_DrvNum-0x7C00]
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 di
popa
add ax, di
adc dx, 0
sub cx, di
jnz do_read_sectors
popa
ret
end if
scan_for_filename:
; in: ds:si -> 11-bytes FAT name
; in: es:0 -> part of directory data
; in: cx = number of entries
; out: if found: CF=0, ZF=1, es:di -> directory entry
; out: if not found, but continue required: CF=1 and ZF=0
; out: if not found and zero item reached: CF=1 and ZF=1
xor di, di
push cx
sloop:
cmp byte [es:di], 0
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
inc cx ; clear ZF flag
snotfound:
stc
sdone:
pop cx
lrdret:
ret
lookup_in_root_dir:
; ss:bp = 0:7C00
; in: ds:si -> 11-bytes FAT name
; out: if found: CF=0, es:di -> directory entry
; out: if not found: CF=1
mov cx, [bp+BPB_RootEntCnt-0x7C00]
push cx
; first, look in root directory cache
push 0x9000
pop es
test ch, ch
jz @f
mov cx, 0x100
@@:
mov ax, [bp-4]
mov dx, [bp-2] ; dx:ax = starting sector of not cached data of root directory
lrdloop:
call scan_for_filename
pop bx
jz lrdret
sub bx, cx
mov cx, bx
stc
jz lrdret
; read no more than 0x10000 bytes, or 0x10000/0x20 = 0x800 entries
push cx
cmp ch, 0x8
jb @f
mov cx, 0x800
@@:
push 0x8000
pop es
push cx
push es
xor bx, bx
add cx, 0xF
shr cx, 4
call read_sectors
pop es
add ax, cx
adc dx, bx
pop cx
jmp lrdloop
out_string:
; in: ds:si -> ASCIIZ string
lodsb
test al, al
jz lrdret
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 F1X'
if use_lba
db 0 ; make bootsector 512 bytes in length
end if
; 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_sectors, read_sectors2, lookup_in_root_dir, scan_for_filename, err_, noloader