kolibrios/kernel/branches/kolibri-cfg/bootloader/fat32/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
; 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