/kernel/trunk/sec_loader/trunk/boot/fat1x/bootsect.asm |
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0,0 → 1,392 |
; 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 |
/kernel/trunk/sec_loader/trunk/boot/fat1x/bootsect.txt |
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0,0 → 1,360 |
; 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. |
;***************************************************************************** |
Âñòðå÷àþòñÿ âèðóñ è FAT. |
- Ïðèâåò, òû êòî? |
- ß? Âèðóñ. |
- A ÿ AFT, òî åñòü TAF, òî åñòü FTA, ÷åðò, ñîâñåì çàïóòàëñÿ... |
Áóòñåêòîð äëÿ FAT12/FAT16-òîìà íà íîñèòåëå ñ ðàçìåðîì ñåêòîðà 0x200 = 512 áàéò. |
===================================================================== |
Åñòü äâå âåðñèè â çàâèñèìîñòè îò òîãî, ïîääåðæèâàåò ëè íîñèòåëü LBA, |
âûáîð îñóùåñòâëÿåòñÿ óñòàíîâêîé êîíñòàíòû use_lba â ïåðâîé ñòðîêå èñõîäíèêà. |
Òðåáîâàíèÿ äëÿ ðàáîòû: |
1) Ñàì áóòñåêòîð, ïåðâàÿ êîïèÿ FAT è âñå èñïîëüçóåìûå ôàéëû |
äîëæíû áûòü ÷èòàáåëüíû. |
2) Ìèíèìàëüíûé ïðîöåññîð - 80186. |
3) Â ñèñòåìå äîëæíî áûòü êàê ìèíèìóì 592K ñâîáîäíîé áàçîâîé ïàìÿòè. |
===================================================================== |
Äîêóìåíòàöèÿ â òåìó (ññûëêè âàëèäíû íà ìîìåíò íàïèñàíèÿ ýòîãî ôàéëà, 15.05.2008): |
îôèöèàëüíàÿ ñïåöèôèêàöèÿ FAT: http://www.microsoft.com/whdc/system/platform/firmware/fatgen.mspx |
â ôîðìàòå PDF: http://staff.washington.edu/dittrich/misc/fatgen103.pdf |
ðóññêèé ïåðåâîä: http://wasm.ru/docs/11/fatgen103-rus.zip |
îôèöèàëüíàÿ ñïåöèôèêàöèÿ ðàñøèðåíèÿ EDD BIOS 3.0: http://www.phoenix.com/NR/rdonlyres/19FEBD17-DB40-413C-A0B1-1F3F560E222F/0/specsedd30.pdf |
òî æå, âåðñèÿ 1.1: http://www.phoenix.com/NR/rdonlyres/9BEDED98-6B3F-4DAC-BBB7-FA89FA5C30F0/0/specsedd11.pdf |
îïèñàíèå ôóíêöèé BIOS: Interrupt List by Ralf Brown: http://www.cs.cmu.edu/~ralf/files.html |
îôèöèàëüíàÿ ñïåöèôèêàöèÿ Boot BIOS: http://www.phoenix.com/NR/rdonlyres/56E38DE2-3E6F-4743-835F-B4A53726ABED/0/specsbbs101.pdf |
===================================================================== |
Ìàêñèìàëüíîå êîëè÷åñòâî êëàñòåðîâ íà FAT12-òîìå - 0xFF4 = 4084; êàæäûé êëàñòåð |
çàíèìàåò 12 áèò â òàáëèöå FAT, òàê ÷òî îáùèé ðàçìåð íå ïðåâîñõîäèò |
0x17EE = 6126 áàéò. Âñÿ òàáëèöà ïîìåùàåòñÿ â ïàìÿòè. |
Ìàêñèìàëüíîå êîëè÷åñòâî êëàñòåðîâ íà FAT16-òîìå - 0xFFF4 = 65524; êàæäûé |
êëàñòåð çàíèìàåò 16 áèò â òàáëèöå FAT, òàê ÷òî îáùèé ðàçìåð íå ïðåâîñõîäèò |
0x1FFE8 = 131048 áàéò. Âñÿ òàáëèöà òàêæå ïîìåùàåòñÿ â ïàìÿòè, îäíàêî â |
ýòîì ñëó÷àå íåñêîëüêî íåöåëåñîîáðàçíî ñ÷èòûâàòü âñþ òàáëèöó, ïîñêîëüêó |
íà ïðàêòèêå íóæíà òîëüêî íåáîëüøàÿ å¸ ÷àñòü. Ïîýòîìó ìåñòî â ïàìÿòè |
ðåçåðâèðóåòñÿ, íî äàííûå ñ÷èòûâàþòñÿ òîëüêî â ìîìåíò, êîãäà ê íèì |
äåéñòâèòåëüíî èä¸ò îáðàùåíèå. |
Ñõåìà èñïîëüçóåìîé ïàìÿòè: |
...-7C00 ñòåê |
7C00-7E00 êîä áóòñåêòîðà |
7E00-8200 âñïîìîãàòåëüíûé ôàéë çàãðóç÷èêà (kordldr.f1x) |
8200-8300 ñïèñîê çàãðóæåííûõ ñåêòîðîâ òàáëèöû FAT16 |
(1 = ñîîòâåòñòâóþùèé ñåêòîð çàãðóæåí) |
60000-80000 çàãðóæåííàÿ òàáëèöà FAT12 / ìåñòî äëÿ òàáëèöû FAT16 |
80000-90000 òåêóùèé êëàñòåð òåêóùåé ðàññìàòðèâàåìîé ïàïêè |
90000-92000 êýø äëÿ êîðíåâîé ïàïêè |
92000-... êýø äëÿ íåêîðíåâûõ ïàïîê (êàæäîé ïàïêå îòâîäèòñÿ |
2000h áàéò = 100h âõîäîâ, îäíîâðåìåííî â êýøå |
ìîæåò íàõîäèòüñÿ íå áîëåå 7 ïàïîê; |
òî÷íûé ðàçìåð îïðåäåëÿåòñÿ ðàçìåðîì äîñòóïíîé |
ôèçè÷åñêîé ïàìÿòè - êàê ïðàâèëî, íåïîñðåäñòâåííî |
ïåðåä A0000 ðàçìåùàåòñÿ EBDA, Extended BIOS Data Area) |
===================================================================== |
Îñíîâíîé ïðîöåññ çàãðóçêè. |
Òî÷êà âõîäà (start): ïîëó÷àåò óïðàâëåíèå îò BIOS ïðè çàãðóçêå, ïðè ýòîì |
dl ñîäåðæèò èäåíòèôèêàòîð äèñêà, ñ êîòîðîãî èä¸ò çàãðóçêà |
1. Íàñòðàèâàåò ñòåê ss:sp = 0:7C00 (ñòåê ðàñïîëàãàåòñÿ íåïîñðåäñòâåííî ïåðåä |
êîäîì), ñåãìåíò äàííûõ ds = 0, è óñòàíàâëèâàåò ss:bp íà íà÷àëî |
áóòñåêòîðà (â äàëüíåéøåì äàííûå áóäóò àäðåñîâàòüñÿ ÷åðåç [bp+N] - |
ýòî îñâîáîæäàåò ds è ýêîíîìèò íà ðàçìåðå êîäà). |
2. LBA-âåðñèÿ: ïðîâåðÿåò, ïîääåðæèâàåò ëè íîñèòåëü LBA, âûçîâîì ôóíêöèè 41h |
ïðåðûâàíèÿ 13h. Åñëè íåò, ïåðåõîäèò íà êîä îáðàáîòêè îøèáîê ñ |
ñîîáùåíèåì îá îòñóòñòâèè LBA. |
CHS-âåðñèÿ: îïðåäåëÿåò ãåîìåòðèþ íîñèòåëÿ âûçîâîì ôóíêöèè 8 ïðåðûâàíèÿ 13h è |
çàïèñûâàåò ïîëó÷åííûå äàííûå ïîâåðõ BPB. Åñëè âûçîâ çàâåðøèëñÿ îøèáêîé, |
ïðåäïîëàãàåò óæå ñóùåñòâóþùèå äàííûå êîððåêòíûìè. |
3. Âû÷èñëÿåò íåêîòîðûå ïàðàìåòðû FAT-òîìà: íà÷àëüíûé ñåêòîð êîðíåâîé ïàïêè |
è íà÷àëüíûé ñåêòîð äàííûõ. Êëàä¸ò èõ â ñòåê; âïîñëåäñòâèè îíè |
âñåãäà áóäóò ëåæàòü â ñòåêå è àäðåñîâàòüñÿ ÷åðåç bp. |
4. Ñ÷èòûâàåò íà÷àëî êîðíåâîé ïàïêè ïî àäðåñó 9000:0000. ×èñëî ñ÷èòûâàåìûõ |
ñåêòîðîâ - ìèíèìóì èç ðàçìåðà êîðíåâîé ïàïêè, óêàçàííîãî â BPB, è 16 |
(ðàçìåð êýøà äëÿ êîðíåâîé ïàïêè - 2000h áàéò = 16 ñåêòîðîâ). |
5. Èùåò â êîðíåâîé ïàïêå ýëåìåíò kordldr.f1x. Åñëè íå íàõîäèò, èëè åñëè |
îí îêàçûâàåòñÿ ïàïêîé, èëè åñëè ôàéë èìååò íóëåâóþ äëèíó - |
ïåðåõîäèò íà êîä îáðàáîòêè îøèáîê ñ ñîîáùåíèåì î |
íåíàéäåííîì çàãðóç÷èêå. |
Çàìå÷àíèå: íà ýòîì ýòàïå çàãðóçêè èñêàòü ìîæíî òîëüêî â êîðíåâîé |
ïàïêå è òîëüêî èìåíà, çàäàííûå â ôîðìàòå ôàéëîâîé ñèñòåìå FAT |
(8+3 - 8 áàéò íà èìÿ, 3 áàéòà íà ðàñøèðåíèå, âñå áóêâû äîëæíû |
áûòü çàãëàâíûìè, ïðè íåîáõîäèìîñòè èìÿ è ðàñøèðåíèå äîïîëíÿþòñÿ |
ïðîáåëàìè, ðàçäåëÿþùåé òî÷êè íåò, çàâåðøàþùåãî íóëÿ íåò). |
6. Çàãðóæàåò ïåðâûé êëàñòåð ôàéëà kordldr.f1x ïî àäðåñó 0:7E00 è ïåðåäà¸ò |
åìó óïðàâëåíèå. Ïðè ýòîì â ðåãèñòðàõ dx:ax îêàçûâàåòñÿ àáñîëþòíûé |
íîìåð ïåðâîãî ñåêòîðà kordldr.f1x, à â cx - ÷èñëî ñ÷èòàííûõ ñåêòîðîâ |
(ðàâíîå ðàçìåðó êëàñòåðà). |
Âñïîìîãàòåëüíûå ïðîöåäóðû áóòñåêòîðà. |
Êîä îáðàáîòêè îøèáîê (err): |
1. Âûâîäèò ñòðîêó ñ ñîîáùåíèåì îá îøèáêå. |
2. Âûâîäèò ñòðîêó "Press any key...". |
3. Æä¸ò íàæàòèÿ any key. |
4. Âûçûâàåò int 18h, äàâàÿ øàíñ BIOSó ïîïûòàòüñÿ çàãðóçèòüñÿ îòêóäà-íèáóäü åù¸. |
5. Äëÿ ïîäñòðàõîâêè çàöèêëèâàåòñÿ. |
Ïðîöåäóðà ÷òåíèÿ ñåêòîðîâ (read_sectors è read_sectors2): |
íà âõîäå äîëæíî áûòü óñòàíîâëåíî: |
ss:bp = 0:7C00 |
es:bx = óêàçàòåëü íà íà÷àëî áóôåðà, êóäà áóäóò ïðî÷èòàíû äàííûå |
dx:ax = ñòàðòîâûé ñåêòîð (îòíîñèòåëüíî íà÷àëà ëîãè÷åñêîãî äèñêà |
äëÿ read_sectors, îòíîñèòåëüíî íà÷àëà äàííûõ äëÿ read_sectors2) |
cx = ÷èñëî ñåêòîðîâ (äîëæíî áûòü áîëüøå íóëÿ) |
íà âûõîäå: es:bx óêàçûâàåò íà êîíåö áóôåðà, â êîòîðûé áûëè ïðî÷èòàíû äàííûå |
0. Åñëè âûçûâàåòñÿ read_sectors2, îíà ïåðåâîäèò óêàçàííûé åé íîìåð ñåêòîðà |
â íîìåð îòíîñèòåëüíî íà÷àëà ëîãè÷åñêîãî äèñêà, ïðèáàâëÿÿ íîìåð ñåêòîðà |
íà÷àëà äàííûõ, õðàíÿùèéñÿ â ñòåêå êàê [bp-8]. |
1. Ïåðåâîäèò ñòàðòîâûé ñåêòîð (îòñ÷èòûâàåìûé îò íà÷àëà òîìà) â ñåêòîð íà |
óñòðîéñòâå, ïðèáàâëÿÿ çíà÷åíèå ñîîòâåòñòâóþùåãî ïîëÿ èç BPB. |
2.  öèêëå (øàãè 3-6) ÷èòàåò ñåêòîðû, ñëåäèò çà òåì, ÷òîáû íà êàæäîé èòåðàöèè |
CHS-âåðñèÿ: âñå ÷èòàåìûå ñåêòîðû áûëè íà îäíîé äîðîæêå. |
LBA-âåðñèÿ: ÷èñëî ÷èòàåìûõ ñåêòîðîâ íå ïðåâîñõîäèëî 7Fh (òðåáîâàíèå |
ñïåöèôèêàöèè EDD BIOS). |
CHS-âåðñèÿ: |
3. Ïåðåâîäèò àáñîëþòíûé íîìåð ñåêòîðà â CHS-ñèñòåìó: ñåêòîð ðàññ÷èòûâàåòñÿ êàê |
åäèíèöà ïëþñ îñòàòîê îò äåëåíèÿ àáñîëþòíîãî íîìåðà íà ÷èñëî ñåêòîðîâ |
íà äîðîæêå; äîðîæêà ðàññ÷èòûâàåòñÿ êàê îñòàòîê îò äåëåíèÿ ÷àñòíîãî, |
ïîëó÷åííîãî íà ïðåäûäóùåì øàãå, íà ÷èñëî äîðîæåê, à öèëèíäð - êàê |
÷àñòíîå îò ýòîãî æå äåëåíèÿ. Åñëè ÷èñëî ñåêòîðîâ äëÿ ÷òåíèÿ áîëüøå, |
÷åì ÷èñëî ñåêòîðîâ äî êîíöà äîðîæêè, óìåíüøàåò ÷èñëî ñåêòîðîâ äëÿ |
÷òåíèÿ. |
4. Ôîðìèðóåò äàííûå äëÿ âûçîâà int 13h (ah=2 - ÷òåíèå, al=÷èñëî ñåêòîðîâ, |
dh=ãîëîâêà, (ìëàäøèå 6 áèò cl)=ñåêòîð, |
(ñòàðøèå 2 áèòà cl è âåñü ch)=äîðîæêà, dl=äèñê, es:bx->áóôåð). |
5. Âûçûâàåò BIOS. Åñëè BIOS ðàïîðòóåò îá îøèáêå, âûïîëíÿåò ñáðîñ äèñêà |
è ïîâòîðÿåò ïîïûòêó ÷òåíèÿ, âñåãî äåëàåòñÿ íå áîëåå òð¸õ ïîïûòîê |
(íåñêîëüêî ïîïûòîê íóæíî â ñëó÷àå äèñêåòû äëÿ ãàðàíòèè òîãî, ÷òî |
ìîòîð ðàñêðóòèëñÿ). Åñëè âñå òðè ðàçà ïðîèñõîäèò îøèáêà ÷òåíèÿ, |
ïåðåõîäèò íà êîä îáðàáîòêè îøèáîê ñ ñîîáùåíèåì "Read error". |
6.  ñîîòâåòñòâèè ñ ÷èñëîì ïðî÷èòàííûõ íà òåêóùåé èòåðàöèè ñåêòîðîâ |
êîððåêòèðóåò òåêóùèé ñåêòîð, ÷èñëî îñòàâøèõñÿ ñåêòîðîâ è óêàçàòåëü íà |
áóôåð (â ïàðå es:bx êîððåêòèðóåòñÿ es). Åñëè âñ¸ ïðî÷èòàíî, çàêàí÷èâàåò |
ðàáîòó, èíà÷å âîçâðàùàåòñÿ íà øàã 3. |
LBA-âåðñèÿ: |
3. Åñëè ÷èñëî ñåêòîðîâ äëÿ ÷òåíèÿ áîëüøå 7Fh, óìåíüøàåò åãî (äëÿ òåêóùåé |
èòåðàöèè) äî 7Fh. |
4. Ôîðìèðóåò â ñòåêå ïàêåò äëÿ int 13h (êëàä¸ò âñå íóæíûå äàííûå êîìàíäàìè |
push, ïðè÷¸ì â îáðàòíîì ïîðÿäêå: ñòåê - ñòðóêòóðà LIFO, è äàííûå â |
ñòåêå õðàíÿòñÿ â îáðàòíîì ïîðÿäêå ïî îòíîøåíèþ ê òîìó, êàê èõ òóäà |
êëàëè). |
5. Âûçûâàåò BIOS. Åñëè BIOS ðàïîðòóåò îá îøèáêå, ïåðåõîäèò íà êîä îáðàáîòêè |
îøèáîê ñ ñîîáùåíèåì "Read error". Î÷èùàåò ñòåê îò ïàêåòà, |
ñôîðìèðîâàííîãî íà ïðåäûäóùåì øàãå. |
6.  ñîîòâåòñòâèè ñ ÷èñëîì ïðî÷èòàííûõ íà òåêóùåé èòåðàöèè ñåêòîðîâ |
êîððåêòèðóåò òåêóùèé ñåêòîð, ÷èñëî îñòàâøèõñÿ ñåêòîðîâ è óêàçàòåëü íà |
áóôåð (â ïàðå es:bx êîððåêòèðóåòñÿ es). Åñëè âñ¸ ïðî÷èòàíî, çàêàí÷èâàåò |
ðàáîòó, èíà÷å âîçâðàùàåòñÿ íà øàã 3. |
Ïðîöåäóðà ïîèñêà ýëåìåíòà ïî èìåíè â óæå ïðî÷èòàííûõ äàííûõ ïàïêè |
(scan_for_filename): |
íà âõîäå äîëæíî áûòü óñòàíîâëåíî: |
ds:si = óêàçàòåëü íà èìÿ ôàéëà â ôîðìàòå FAT (11 áàéò, 8 íà èìÿ, |
3 íà ðàñøèðåíèå, âñå áóêâû çàãëàâíûå, åñëè èìÿ/ðàñøèðåíèå |
êîðî÷å, îíî äîïîëíÿåòñÿ äî ìàêñèìóìà ïðîáåëàìè) |
es = ñåãìåíò äàííûõ ïàïêè |
cx = ÷èñëî ýëåìåíòîâ â ïðî÷èòàííûõ äàííûõ |
íà âûõîäå: ZF îïðåäåëÿåò, íóæíî ëè ïðîäîëæàòü ðàçáîð äàííûõ ïàïêè |
(ZF=1, åñëè ëèáî íàéäåí çàïðîøåííûé ýëåìåíò, ëèáî äîñòèãíóò |
êîíåö ïàïêè); CF îïðåäåëÿåò, óäàëîñü ëè íàéòè ýëåìåíò ñ èñêîìûì èìåíåì |
(CF=1, åñëè íå óäàëîñü); åñëè óäàëîñü, òî es:di óêàçûâàåò íà íåãî. |
scan_for_filename ñ÷èòàåò, ÷òî äàííûå ïàïêè ðàçìåùàþòñÿ íà÷èíàÿ ñ es:0. |
Ïåðâîé êîìàíäîé ïðîöåäóðà îáíóëÿåò di. Çàòåì ïðîñòî â öèêëå ïî ýëåìåíòàì ïàïêè |
ïðîâåðÿåò èìåíà. |
Ïðîöåäóðà ïîèñêà ýëåìåíòà â êîðíåâîé ïàïêå (lookup_in_root_dir): |
íà âõîäå äîëæíî áûòü óñòàíîâëåíî: |
ss:bp = 0:7C00 |
ds:si = óêàçàòåëü íà èìÿ ôàéëà â ôîðìàòå FAT (ñì. âûøå) |
íà âûõîäå: ôëàã CF îïðåäåëÿåò, óäàëîñü ëè íàéòè ôàéë; åñëè óäàëîñü, òî |
CF ñáðîøåí è es:di óêàçûâàåò íà ýëåìåíò ïàïêè |
Íà÷èíàåò ñ ïðîñìîòðà êýøèðîâàííîé (íà÷àëüíîé) ÷àñòè êîðíåâîé ïàïêè.  öèêëå |
ñêàíèðóåò ýëåìåíòû; åñëè ïî ðåçóëüòàòàì ñêàíèðîâàíèÿ îáíàðóæèâàåò, |
÷òî íóæíî ÷èòàòü ïàïêó äàëüøå, òî ñ÷èòûâàåò íå áîëåå 0x10000 = 64K |
áàéò (îãðàíè÷åíèå ââåäåíî ïî äâóì ïðè÷èíàì: âî-ïåðâûõ, ÷òîáû çàâåäîìî |
íå âûëåçòè çà ïðåäåëû èñïîëüçóåìîé ïàìÿòè, âî-âòîðûõ, ñêàíèðîâàíèå |
ïðåäïîëàãàåò, ÷òî âñå îáðàáàòûâàåìûå ýëåìåíòû ðàñïîëàãàþòñÿ â îäíîì |
ñåãìåíòå) è ïðîäîëæàåò öèêë. |
Ñêàíèðîâàíèå ïðåêðàùàåòñÿ â òð¸õ ñëó÷àÿõ: îáíàðóæåí èñêîìûé ýëåìåíò; |
êîí÷èëèñü ýëåìåíòû â ïàïêå (ñóäÿ ïî ÷èñëó ýëåìåíòîâ, óêàçàííîìó â BPB); |
î÷åðåäíîé ýëåìåíò ïàïêè ñèãíàëèçèðóåò î êîíöå (ïåðâûé áàéò íóëåâîé). |
Ïðîöåäóðà âûâîäà íà ýêðàí ASCIIZ-ñòðîêè (out_string): |
íà âõîäå: ds:si -> ñòðîêà |
 öèêëå, ïîêà íå äîñòèãíóò çàâåðøàþùèé íîëü, âûçûâàåò ôóíêöèþ int 10h/ah=0Eh. |
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Ðàáîòà âñïîìîãàòåëüíîãî çàãðóç÷èêà kordldr.f1x: |
1. Îïðåäåëÿåò, áûë ëè îí çàãðóæåí CHS- èëè LBA-âåðñèåé áóòñåêòîðà. |
 çàâèñèìîñòè îò ýòîãî óñòàíàâëèâàåò ñìåùåíèÿ èñïîëüçóåìûõ ïðîöåäóð |
áóòñåêòîðà. Êðèòåðèé ïðîâåðêè: scan_for_filename äîëæíà íà÷èíàòüñÿ |
ñ èíñòðóêöèè 'xor di,di' ñ êîäîì 31 FF (âîîáùå-òî ýòà èíñòðóêöèÿ ìîæåò |
ñ ðàâíûì óñïåõîì àññåìáëèðîâàòüñÿ è êàê 33 FF, íî fasm ãåíåðèðóåò |
èìåííî òàêóþ ôîðìó). |
2. Óçíà¸ò ðàçìåð ñâîáîäíîé áàçîâîé ïàìÿòè (ò.å. ñâîáîäíîãî íåïðåðûâíîãî êóñêà |
àäðåñîâ ïàìÿòè, íà÷èíàþùåãîñÿ ñ 0) âûçîâîì int 12h.  ñîîòâåòñòâèè ñ |
íèì âû÷èñëÿåò ÷èñëî ýëåìåíòîâ â êýøå ïàïîê. Õîòÿ áû äëÿ îäíîãî ýëåìåíòà |
ìåñòî äîëæíî áûòü, îòñþäà îãðàíè÷åíèå â 592 Kb (94000h áàéò). |
Çàìå÷àíèå: ýòîò ðàçìåð íå ìîæåò ïðåâîñõîäèòü 0A0000h áàéò è |
íà ïðàêòèêå îêàçûâàåòñÿ íåìíîãî (íà 1-2 êèëîáàéòà) ìåíüøèì èç-çà |
íàëè÷èÿ äîïîëíèòåëüíîé îáëàñòè äàííûõ BIOS "ââåðõó" áàçîâîé ïàìÿòè. |
3. Îïðåäåëÿåò òèï ôàéëîâîé ñèñòåìû: FAT12 èëè FAT16. Ñîãëàñíî îôèöèàëüíîé |
ñïåöèôèêàöèè îò Microsoft (âåðñèÿ 1.03 ñïåöèôèêàöèè äàòèðîâàíà, |
ê ñëîâó, 06 äåêàáðÿ 2000 ãîäà), ðàçðÿäíîñòü FAT îïðåäåëÿåòñÿ |
èñêëþ÷èòåëüíî ÷èñëîì êëàñòåðîâ: ìàêñèìàëüíîå ÷èñëî êëàñòåðîâ íà |
FAT12-òîìå ðàâíî 4094 = 0xFF4. Ñîãëàñíî çäðàâîìó ñìûñëó, íà FAT12 |
ìîæåò áûòü 0xFF5 êëàñòåðîâ, íî íå áîëüøå: êëàñòåðû íóìåðóþòñÿ ñ 2, |
à ÷èñëî 0xFF7 íå ìîæåò áûòü êîððåêòíûì íîìåðîì êëàñòåðà. |
Win95/98/Me ñëåäóåò çäðàâîìó ñìûñëó: ðàçãðàíè÷åíèå FAT12/16 äåëàåòñÿ |
ïî ìàêñèìóìó 0xFF5. Äðàéâåð FAT â WinNT/2k/XP/Vista âîîáùå ïîñòóïàåò |
ÿâíî íåâåðíî, ñ÷èòàÿ, ÷òî 0xFF6 (èëè ìåíüøå) êëàñòåðîâ îçíà÷àåò |
FAT12-òîì, â ðåçóëüòàòå ïîëó÷àåòñÿ, ÷òî ïîñëåäíèé êëàñòåð |
(â ñëó÷àå 0xFF6) íåàäðåñóåì. Îñíîâíîé çàãðóç÷èê osloader.exe |
[âñòðîåí â ntldr] äëÿ NT/2k/XP äåëàåò òàê æå. Ïåðâè÷íûé çàãðóç÷èê |
[áóòñåêòîð FAT12/16 çàãðóæàåò ïåðâûé ñåêòîð ntldr, è ðàçáîð FAT-òàáëèöû |
ëåæèò íà í¸ì] â NT/2k ïîäâåðæåí òîé æå îøèáêå.  XP å¸ òàêè èñïðàâèëè |
â ñîîòâåòñòâèè ñî ñïåöèôèêàöèåé. Linux ïðè îïðåäåëåíèè FAT12/FAT16 |
÷åñòíî ñëåäóåò ñïåöèôèêàöèè. |
Çäåñü êîä îñíîâàí âñ¸ æå íà ñïåöèôèêàöèè. 9x ìåðòâà, à â ëèíåéêå NT |
Microsoft åñëè è áóäåò èñïðàâëÿòü îøèáêè, òî ñîãëàñíî ñîáñòâåííîìó |
îïèñàíèþ. |
4. Äëÿ FAT12: çàãðóæàåò â ïàìÿòü ïåðâóþ êîïèþ òàáëèöû FAT ïî àäðåñó 6000:0000. |
Åñëè ðàçìåð, óêàçàííûé â BPB, ïðåâîñõîäèò 12 ñåêòîðîâ, |
ýòî îçíà÷àåò, ÷òî çàÿâëåííûé ðàçìåð ñëèøêîì áîëüøîé (ýòî íå ñ÷èòàåòñÿ |
îøèáêîé ôàéëîâîé ñèñòåìû), è ÷èòàþòñÿ òîëüêî 12 ñåêòîðîâ (òàáëèöà FAT12 |
çàâåäîìî âëåçàåò â òàêîé îáú¸ì äàííûõ). |
Äëÿ FAT16: èíèöèàëèçèðóåò âíóòðåííèå äàííûå, óêàçûâàÿ, ÷òî íèêàêîé ñåêòîð |
FAT íå çàãðóæåí (îíè áóäóò ïîäãðóæàòüñÿ ïîçäíåå, êîãäà ïîíàäîáÿòñÿ |
è òîëüêî òå, êîòîðûå ïîíàäîáÿòñÿ). |
5. Åñëè êëàñòåð ðàâåí ñåêòîðó, òî áóòñåêòîð çàãðóçèë òîëüêî ÷àñòü ôàéëà |
kordldr.f1x, è çàãðóç÷èê ïîäãðóæàåò âòîðóþ ñâîþ ÷àñòü, èñïîëüçóÿ |
çíà÷åíèÿ ðåãèñòðîâ íà âõîäå â kordldr.f1x. |
6. Çàãðóæàåò âòîðè÷íûé çàãðóç÷èê kord/loader ïî àäðåñó 1000:0000. Åñëè ôàéë íå |
íàéäåí, èëè îêàçàëñÿ ïàïêîé, èëè îêàçàëñÿ ñëèøêîì áîëüøèì, òî ïåðåõîäèò |
íà êîä îáðàáîòêè îøèáîê èç áóòñåêòîðà ñ ñîîáùåíèåì |
"Fatal error: cannot load the secondary loader". |
Çàìå÷àíèå: íà ýòîì ýòàïå èìÿ ôàéëà óæå ìîæíî óêàçûâàòü âìåñòå ñ ïóò¸ì |
è â ôîðìàòå ASCIIZ, õîòÿ ïîääåðæêè äëèííûõ èì¸í è íåàíãëèéñêèõ ñèìâîëîâ |
ïî-ïðåæíåìó íåò. |
7. Èçìåíÿåò êîä îáðàáîòêè îøèáîê áóòñåêòîðà íà ïåðåõîä íà ìåòêó hooked_err. |
Ýòî íóæíî, ÷òîáû ïîñëåäóþùèå îáðàùåíèÿ ê êîäó áóòñåêòîðà â ñëó÷àå |
îøèáîê ÷òåíèÿ íå âûâîäèë ñîîòâåòñòâóþùåå ñîîáùåíèå ñ ïîñëåäóþùåé |
ïåðåçàãðóçêîé, à ðàïîðòîâàë îá îøèáêå ÷òåíèÿ, êîòîðóþ ìîã áû |
êàê-íèáóäü îáðàáîòàòü âòîðè÷íûé çàãðóç÷èê. |
8. Åñëè çàãðóçî÷íûé äèñê èìååò èäåíòèôèêàòîð ìåíüøå 0x80, |
òî óñòàíàâëèâàåò al='f' ("floppy"), ah=èäåíòèôèêàòîð äèñêà, |
èíà÷å al='h' ("hard"), ah=èäåíòèôèêàòîð äèñêà-0x80 (íîìåð äèñêà). |
Óñòàíàâëèâàåò bx='12', åñëè òèï ôàéëîâîé ñèñòåìû - FAT12, è |
bx='16' â ñëó÷àå FAT16. Óñòàíàâëèâàåò si=ñìåùåíèå ôóíêöèè îáðàòíîãî |
âûçîâà. Ïîñêîëüêó â ýòîò ìîìåíò ds=0, òî ds:si îáðàçóþò ïîëíûé àäðåñ. |
9. Ïåðåäà¸ò óïðàâëåíèå ïî àäðåñó 1000:0000. |
Ôóíêöèÿ îáðàòíîãî âûçîâà äëÿ âòîðè÷íîãî çàãðóç÷èêà: |
ïðåäîñòàâëÿåò âîçìîæíîñòü ÷òåíèÿ ôàéëà. |
Âõîä è âûõîä îïèñàíû â ñïåöèôèêàöèè íà çàãðóç÷èê. |
1. Ñîõðàíÿåò ñòåê âûçûâàþùåãî êîäà è óñòàíàâëèâàåò ñâîé ñòåê: |
ss:sp = 0:(7C00-8), bp=7C00: ïàðà ss:bp ïðè ðàáîòå ñ îñòàëüíûì |
êîäîì äîëæíà óêàçûâàòü íà 0:7C00, à -8 áåð¸òñÿ îò òîãî, ÷òî |
èíèöèàëèçèðóþùèé êîä áóòñåêòîðà óæå ïîìåñòèë â ñòåê 2 äâîéíûõ ñëîâà, |
è îíè äîëæíû ñîõðàíÿòüñÿ â íåèçìåííîñòè. |
2. Ðàçáèðàåò ïåðåäàííûå ïàðàìåòðû, âûÿñíÿåò, êàêîå äåéñòâèå çàïðîøåíî, |
è âûçûâàåò íóæíóþ âñïîìîãàòåëüíóþ ïðîöåäóðó. |
3. Âîññòàíàâëèâàåò ñòåê âûçûâàþùåãî êîäà è âîçâðàùàåò óïðàâëåíèå. |
Âñïîìîãàòåëüíûå ïðîöåäóðû kordldr.f1x. |
Ïðîöåäóðà ïîëó÷åíèÿ ñëåäóþùåãî êëàñòåðà â FAT (get_next_cluster): |
1. Âñïîìèíàåò ðàçðÿäíîñòü FAT, âû÷èñëåííóþ ðàíåå. |
Äëÿ FAT12: |
2. Óñòàíàâëèâàåò ds = 0x6000 - ñåãìåíò, êóäà ðàíåå áûëà ñ÷èòàíà |
âñÿ òàáëèöà FAT. |
3. Ïîäñ÷èòûâàåò si = (êëàñòåð) + (êëàñòåð)/2 - ñìåùåíèå â ýòîì ñåãìåíòå |
ñëîâà, çàäàþùåãî ñëåäóþùèé êëàñòåð. Çàãðóæàåò ñëîâî ïî ýòîìó àäðåñó. |
4. Åñëè êëàñòåð èìååò íå÷¸òíûé íîìåð, òî ñîîòâåòñòâóþùèé åìó ýëåìåíò |
ðàñïîëàãàåòñÿ â ñòàðøèõ 12 áèòàõ ñëîâà, è ñëîâî íóæíî ñäâèíóòü âïðàâî |
íà 4 áèòà; â ïðîòèâíîì ñëó÷àå - â ìëàäøèõ 12 áèòàõ, è äåëàòü íè÷åãî íå |
íàäî. |
5. Âûäåëÿåò èç ïîëó÷èâøåãîñÿ ñëîâà 12 áèò. Ñðàâíèâàåò èõ ñ ïðåäåëîì 0xFF7: |
íîìåðà íîðìàëüíûõ êëàñòåðîâ ìåíüøå, è ôëàã CF óñòàíàâëèâàåòñÿ; |
ñïåöèàëüíûå çíà÷åíèÿ EOF è BadClus ñáðàñûâàþò ôëàã CF. |
Äëÿ FAT16: |
2. Âû÷èñëÿåò àäðåñ ïàìÿòè, ïðåäíàçíà÷åííîé äëÿ ñîîòâåòñòâóþùåãî ñåêòîðà äàííûõ |
â òàáëèöå FAT. |
3. Åñëè ñåêòîð åù¸ íå çàãðóæåí, òî çàãðóæàåò åãî. |
4. Âû÷èñëÿåò ñìåùåíèå äàííûõ äëÿ êîíêðåòíîãî êëàñòåðà îòíîñèòåëüíî íà÷àëà |
ñåêòîðà. |
5. Çàãðóæàåò ñëîâî â ax èç àäðåñà, âû÷èñëåííîìó íà øàãàõ 1 è 3. |
6. Ñðàâíèâàåò åãî ñ ïðåäåëîì 0xFFF7: íîìåðà íîðìàëüíûõ êëàñòåðîâ ìåíüøå, è ôëàã |
CF óñòàíàâëèâàåòñÿ; ñïåöèàëüíûå çíà÷åíèÿ EOF è BadClus ñáðàñûâàþò CF. |
Ïðîöåäóðà çàãðóçêè ôàéëà (load_file): |
1. Òåêóùàÿ ðàññìàòðèâàåìàÿ ïàïêà - êîðíåâàÿ. Â öèêëå âûïîëíÿåò øàãè 2-4. |
2. Êîíâåðòèðóåò èìÿ òåêóùåãî ðàññìàòðèâàåìîãî êîìïîíåíòà èìåíè (êîìïîíåíòû |
ðàçäåëÿþòñÿ ñèìâîëîì '/') â FAT-ôîðìàò 8+3. Åñëè ýòî íåâîçìîæíî |
(áîëüøå 8 ñèìâîëîâ â èìåíè, áîëüøå 3 ñèìâîëîâ â ðàñøèðåíèè èëè |
áîëüøå îäíîé òî÷êè), âîçâðàùàåòñÿ ñ îøèáêîé. |
3. Èùåò ýëåìåíò ñ òàêèì èìåíåì â òåêóùåé ðàññìàòðèâàåìîé ïàïêå. Äëÿ êîðíåâîé |
ïàïêè èñïîëüçóåòñÿ ïðîöåäóðà èç áóòñåêòîðà. Äëÿ îñòàëüíûõ ïàïîê: |
a) Ïðîâåðÿåò, åñòü ëè òàêàÿ ïàïêà â êýøå íåêîðíåâûõ ïàïîê. |
(Èäåíòèôèêàöèÿ ïàïîê îñóùåñòâëÿåòñÿ ïî íîìåðó íà÷àëüíîãî êëàñòåðà.) |
Åñëè òàêîé ïàïêè åù¸ íåò, äîáàâëÿåò å¸ â êýø; åñëè òîò ïåðåïîëíÿåòñÿ, |
âûêèäûâàåò ïàïêó, ê êîòîðîé äîëüøå âñåãî íå áûëî îáðàùåíèé. (Äëÿ |
êàæäîãî ýëåìåíòà êýøà õðàíèòñÿ ìåòêà îò 0 äî (ðàçìåð êýøà)-1, |
îïðåäåëÿþùàÿ åãî íîìåð ïðè ñîðòèðîâêå ïî äàâíîñòè ïîñëåäíåãî îáðàùåíèÿ. |
Ïðè îáðàùåíèè ê êàêîìó-òî ýëåìåíòó åãî ìåòêà ñòàíîâèòñÿ íóëåâîé, |
à òå ìåòêè, êîòîðûå ìåíüøå ñòàðîãî çíà÷åíèÿ, óâåëè÷èâàþòñÿ íà åäèíèöó.) |
á) Ïðîñìàòðèâàåò â ïîèñêàõ çàïðîøåííîãî èìåíè âñå ýëåìåíòû èç êýøà, |
èñïîëüçóÿ ïðîöåäóðó èç áóòñåêòîðà. Åñëè îáíàðóæèâàåò èñêîìûé ýëåìåíò, |
ïåðåõîäèò ê øàãó 4. Åñëè îáíàðóæèâàåò êîíåö ïàïêè, âîçâðàùàåòñÿ èç |
ïðîöåäóðû ñ îøèáêîé. |
â)  öèêëå ñ÷èòûâàåò ïàïêó ïîñåêòîðíî. Ïðè ýòîì ïðîïóñêàåò íà÷àëüíûå |
ñåêòîðû, êîòîðûå óæå íàõîäÿòñÿ â êýøå è óæå áûëè ïðîñìîòðåíû. Êàæäûé |
ïðî÷èòàííûé ñåêòîð êîïèðóåò â êýø, åñëè òàì åù¸ îñòà¸òñÿ ìåñòî, |
è ïðîñìàòðèâàåò â í¸ì âñå ýëåìåíòû. Ðàáîòàåò, ïîêà íå ñëó÷èòñÿ îäíî èç |
òð¸õ ñîáûòèé: íàéäåí èñêîìûé ýëåìåíò; êîí÷èëèñü êëàñòåðû (ñóäÿ ïî |
öåïî÷êå êëàñòåðîâ â FAT); î÷åðåäíîé ýëåìåíò ïàïêè ñèãíàëèçèðóåò î êîíöå |
(ïåðâûé áàéò íóëåâîé).  äâóõ ïîñëåäíèõ ñëó÷àÿõ âîçâðàùàåòñÿ ñ îøèáêîé. |
4. Ïðîâåðÿåò òèï íàéäåííîãî ýëåìåíòà (ôàéë/ïàïêà): ïîñëåäíèé ýëåìåíò â |
çàïðîøåííîì èìåíè äîëæåí áûòü ôàéëîì, âñå ïðîìåæóòî÷íûå - ïàïêàìè. |
Åñëè òåêóùèé êîìïîíåíò èìåíè - ïðîìåæóòî÷íûé, ïðîäâèãàåò òåêóùóþ |
ðàññìàòðèâàåìóþ ïàïêó è âîçâðàùàåòñÿ ê ïóíêòó 2. |
5. Ïðîõîäèò ïî öåïî÷êå êëàñòåðîâ â FAT è ñ÷èòûâàåò âñå êëàñòåðû â óêàçàííûé |
ïðè âûçîâå áóôåð ïîñëåäîâàòåëüíûìè âûçîâàìè ôóíêöèè áóòñåêòîðà; |
ïðè ýòîì åñëè íåñêîëüêî êëàñòåðîâ ôàéëà ðàñïîëîæåíû íà äèñêå |
ïîñëåäîâàòåëüíî, òî èõ ÷òåíèå îáúåäèíÿåòñÿ â îäíó îïåðàöèþ. |
Ñëåäèò çà òåì, ÷òîáû íå ïðåâûñèòü óêàçàííûé ïðè âûçîâå ïðîöåäóðû |
ëèìèò ÷èñëà ñåêòîðîâ äëÿ ÷òåíèÿ. |
Ïðîöåäóðà ïðîäîëæåíèÿ çàãðóçêè ôàéëà (continue_load_file): âñòðîåíà |
âíóòðü øàãà 5 load_file; çàãðóæàåò â ðåãèñòðû íóæíûå çíà÷åíèÿ (ðàíåå |
ñîõðàí¸ííûå èç load_file) è ïðîäîëæàåò øàã 5. |
/kernel/trunk/sec_loader/trunk/boot/fat1x/kordldr.f1x.asm |
---|
0,0 → 1,667 |
; 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. |
;***************************************************************************** |
org 0x7E00 |
; the KordOS FAT12/FAT16 bootsector loads first cluster of this file to 0:7E00 and transfers control to here |
; ss:bp = 0:7C00 |
virtual at bp |
rb 3 ; BS_jmpBoot |
rb 8 ; BS_OEMName, ignored |
dw ? ; BPB_BytsPerSec |
BPB_SecsPerClus db ? |
BPB_RsvdSecCnt dw ? |
BPB_NumFATs db ? |
BPB_RootEntCnt dw ? |
BPB_TotSec16 dw ? |
db ? ; BPB_Media |
BPB_FATSz16 dw ? |
BPB_SecPerTrk dw ? |
BPB_NumHeads dw ? |
BPB_HiddSec dd ? |
BPB_TotSec32 dd ? |
BS_DrvNum db ? |
fat_type db ? ; this is BS_Reserved1, |
; we use it to save FS type: 0=FAT12, 1=FAT16 |
db ? ; BS_BootSig |
num_sectors dd ? ; BS_VolID |
; rb 11 ; BS_VolLab |
; rb 3 ; BS_FilSysType, first 3 bytes |
read_sectors dw ? |
read_sectors2 dw ? |
lookup_in_root_dir dw ? |
scan_for_filename dw ? |
err dw ? |
noloader dw ? |
cachelimit dw ? |
filesize: ; will be used to save file size |
rb 5 ; BS_FilSysType, last 5 bytes |
; following variables are located in the place of starting code; |
; starting code is no more used at this point |
sect_per_clus dw ? |
cur_cluster dw ? |
next_cluster dw ? |
flags dw ? |
cur_delta dd ? |
end virtual |
; procedures from boot sector |
; LBA version |
lba_read_sectors = 7CE2h |
lba_read_sectors2 = 7CDCh |
lba_lookup_in_root_dir = 7D4Fh |
lba_scan_for_filename = 7D2Dh |
lba_err = 7CB5h |
lba_noloader = 7CB2h |
; CHS version |
chs_read_sectors = 7CDEh |
chs_read_sectors2 = 7CD8h |
chs_lookup_in_root_dir = 7D70h |
chs_scan_for_filename = 7D4Eh |
chs_err = 7CB1h |
chs_noloader = 7CAEh |
push ax cx ; save our position on disk |
push ss |
pop es |
; determine version of bootsector (LBA vs CHS) |
; mov [read_sectors], chs_read_sectors |
; mov [read_sectors2], chs_read_sectors2 |
; mov [lookup_in_root_dir], chs_lookup_in_root_dir |
; mov [scan_for_filename], chs_scan_for_filename |
; mov [err], chs_err |
; mov [noloader], chs_noloader |
lea di, [read_sectors] |
mov si, chs_proc_addresses |
mov cx, 6*2 |
cmp word [chs_scan_for_filename], 0xFF31 ; 'xor di,di' |
jz @f |
add si, cx |
; mov [read_sectors], lba_read_sectors |
; mov [read_sectors2], lba_read_sectors2 |
; mov [lookup_in_root_dir], lba_lookup_in_root_dir |
; mov [scan_for_filename], lba_scan_for_filename |
; mov [err], lba_err |
; mov [noloader], lba_noloader |
@@: |
rep movsb |
mov cl, [BPB_SecsPerClus] |
mov [sect_per_clus], cx |
xor bx, bx |
; determine size of cache for folders |
int 12h ; ax = size of available base memory in Kb |
sub ax, 94000h / 1024 |
jae @f |
nomem: |
mov si, nomem_str |
jmp [err] |
@@: |
shr ax, 3 |
mov [cachelimit], ax ; size of cache - 1 |
; get type of file system - FAT12 or FAT16? |
; calculate number of clusters |
mov ax, [BPB_TotSec16] |
xor dx, dx |
test ax, ax |
jnz @f |
mov ax, word [BPB_TotSec32] |
mov dx, word [BPB_TotSec32+2] |
@@: |
sub ax, [bp-8] ; dword [bp-8] = first data sector |
sbb dx, [bp-6] |
jb j_noloader |
div [sect_per_clus] |
; ax = number of clusters |
; note: this is loader for FAT12/FAT16, so 'div' does not overflow on correct volumes |
mov [fat_type], ch |
cmp ax, 0xFF5 |
jb init_fat12 |
inc [fat_type] |
init_fat16: |
; no sectors loaded |
mov di, 0x8200 |
xor ax, ax |
mov cx, 0x100/2 |
rep stosw |
jmp init_fat_done |
init_fat12: |
; read FAT |
push 0x6000 |
pop es |
mov ax, [BPB_RsvdSecCnt] |
mov cx, [BPB_FATSz16] |
cmp cx, 12 |
jb @f |
mov cx, 12 |
@@: |
xor dx, dx |
call [read_sectors] |
init_fat_done: |
; if cluster = sector, we need to read second part of our file |
; (bootsector loads only first cluster of kordldr.f1x) |
pop cx ax ; restore our position on disk |
cmp cx, 1 |
ja kordldr_full |
sub ax, [bp-8] |
inc ax |
inc ax ; ax = first cluster of kordldr.f12 |
call get_next_cluster |
jc @f |
j_noloader: |
jmp [noloader] |
@@: |
dec ax |
dec ax |
push 0x800 |
pop es |
call [read_sectors2] |
kordldr_full: |
; ...continue loading... |
mov di, secondary_loader_info |
call load_file |
test bx, bx |
mov bx, [err] |
jz @f |
mov si, aKernelNotFound |
jmp bx |
@@: |
; for subsequent calls to callback function, hook error handler |
; mov byte [bx], 0xE9 ; 'jmp' opcode |
; mov ax, hooked_err - 3 |
; sub ax, bx |
; mov word [bx+1], ax |
; push hooked_err / ret |
mov word [bx], 0x68 + ((hooked_err and 0xFF) shl 8) |
mov word [bx+2], (hooked_err shr 8) + (0xC3 shl 8) |
; set registers for secondary loader |
mov ah, [BS_DrvNum] |
mov al, 'f' |
test ah, ah |
jns @f |
sub ah, 80h |
mov al, 'h' |
@@: |
mov bx, '12' |
cmp [fat_type], 0 |
jz @f |
mov bh, '6' |
@@: |
mov si, callback ; ds:si = far pointer to callback procedure |
jmp far [si-callback+secondary_loader_info] ; jump to 1000:0000 |
nomem_str db 'No memory',0 |
chs_proc_addresses: |
dw chs_read_sectors |
dw chs_read_sectors2 |
dw chs_lookup_in_root_dir |
dw chs_scan_for_filename |
dw chs_err |
dw chs_noloader |
lba_proc_addresses: |
dw lba_read_sectors |
dw lba_read_sectors2 |
dw lba_lookup_in_root_dir |
dw lba_scan_for_filename |
dw lba_err |
dw lba_noloader |
get_next_cluster: |
; in: ax = cluster |
; out: if there is next cluster: CF=1, ax = next cluster |
; out: if there is no next cluster: CF=0 |
push si |
cmp [fat_type], 0 |
jnz gnc16 |
; for FAT12 |
push ds |
push 0x6000 |
pop ds |
mov si, ax |
shr si, 1 |
add si, ax |
test al, 1 |
lodsw |
jz @f |
shr ax, 4 |
@@: |
and ax, 0xFFF |
cmp ax, 0xFF7 |
pop ds si |
ret |
; for FAT16 |
gnc16: |
; each sector contains 200h bytes = 100h FAT entries |
; so ah = # of sector, al = offset in sector |
mov si, ax |
mov ah, 0 |
shr si, 8 |
; calculate segment for this sector of FAT table |
; base for FAT table is 6000:0000, so the sector #si has to be loaded to (60000 + 200*si) |
; segment = 6000 + 20*si, offset = 0 |
push es |
push si |
shl si, 5 |
add si, 0x6000 |
mov es, si |
pop si |
cmp byte [ss:0x8200+si], ah ; sector already loaded? |
jnz @f |
; load corresponding sector |
pusha |
push es |
xor bx, bx |
mov ax, [BPB_RsvdSecCnt] |
xor dx, dx |
add ax, si |
adc dx, bx |
mov cx, 1 ; read 1 sector |
call [read_sectors] |
pop es |
popa |
@@: |
mov si, ax |
add si, si |
; mov ax, [es:si] |
lods word [es:si] |
pop es |
cmp ax, 0xFFF7 |
pop si |
ret |
if $ > 0x8000 |
error 'get_next_cluster must fit in first sector of kordldr.f1x!' |
end if |
load_file: |
; in: ss:bp = 0:7C00 |
; in: ds:di -> information structure |
; dw:dw address |
; dw limit in 4Kb blocks (0x1000 bytes) (must be non-zero and not greater than 0x100) |
; ASCIIZ name |
; out: bx = status: bx=0 - ok, bx=1 - file is too big, only part of file was loaded, bx=2 - file not found |
; out: dx:ax = file size (0xFFFFFFFF if file not found) |
xor ax, ax ; start from root directory |
mov dx, -1 |
mov word [filesize], dx |
mov word [filesize+2], dx ; initialize file size with invalid value |
lea si, [di+6] |
parse_dir_loop: |
; convert name to FAT name |
push di |
push ax |
push ss |
pop es |
; convert ASCIIZ filename to FAT name |
mov di, filename |
push di |
mov cx, 8+3 |
mov al, ' ' |
rep stosb |
pop di |
mov cl, 8 ; 8 symbols per name |
mov bl, 1 |
nameloop: |
lodsb |
test al, al |
jz namedone |
cmp al, '/' |
jz namedone |
cmp al, '.' |
jz namedot |
dec cx |
js badname |
cmp al, 'a' |
jb @f |
cmp al, 'z' |
ja @f |
sub al, 'a'-'A' |
@@: |
stosb |
jmp nameloop |
namedot: |
inc bx |
jp badname |
add di, cx |
mov cl, 3 |
jmp nameloop |
badname: ; do not make direct js/jp to notfound_pop: |
; this generates long forms of conditional jumps and results in longer code |
jmp notfound_pop |
namedone: |
; scan directory |
pop ax ; ax = cluster of directory or 0 for root |
push ds |
push si |
push es |
pop ds |
mov si, filename ; ds:si -> filename in FAT style |
test ax, ax |
jnz lookup_in_notroot_dir |
; for root directory, use the subroutine from bootsector |
call [lookup_in_root_dir] |
jmp lookup_done |
lookup_in_notroot_dir: |
; for other directories, read a folder sector-by-sector and scan |
; first, try to use the cache |
push ds |
push cs |
pop ds |
mov bx, [cachelimit] |
add bx, bx |
mov di, foldcache_mark |
@@: |
mov dx, [foldcache_clus+di-foldcache_mark+bx] |
cmp dx, ax |
jz cacheok |
test dx, dx |
jz cacheadd ; the cache has place for new entry |
dec bx |
dec bx |
jns @b |
; the folder is not present in the cache, so add it |
; the cache is full; find the oldest entry and replace it with the new one |
mov dx, [cachelimit] |
@@: |
inc bx |
inc bx |
cmp word [di+bx], dx ; marks have values 0 through [cachelimit] |
jnz @b |
cacheadd: |
or word [di+bx], 0xFFFF ; very big value, it will be changed soon |
mov [foldcache_clus+di-foldcache_mark+bx], ax |
and [foldcache_size+di-foldcache_mark+bx], 0 ; no folder items yet |
cacheok: |
; update cache marks |
mov dx, [di+bx] |
mov cx, [foldcache_size+di-foldcache_mark+bx] |
mov di, [cachelimit] |
add di, di |
cacheupdate: |
cmp [foldcache_mark+di], dx |
adc [foldcache_mark+di], 0 |
dec di |
dec di |
jns cacheupdate |
and [foldcache_mark+bx], 0 |
; done, bx contains (position in cache)*2 |
pop ds |
; mov dx, bx |
; shl dx, 8 ; dx = (position in cache)*0x2000/0x10 |
; add dx, 0x9200 |
lea dx, [bx+0x92] |
xchg dl, dh |
mov es, dx |
jcxz not_in_cache |
call [scan_for_filename] |
jz lookup_done |
not_in_cache: |
; cache miss, read folder data from disk |
mov bx, cx |
shr bx, 4 |
shl cx, 5 |
mov di, cx ; es:di -> free space in cache entry |
; external loop: scan clusters |
folder_next_cluster: |
; internal loop: scan sectors in cluster |
mov cx, [sect_per_clus] |
push ax |
dec ax |
dec ax |
mul cx |
add ax, [bp-8] |
adc dx, [bp-6] ; dx:ax = absolute sector |
folder_next_sector: |
; skip first bx sectors |
dec bx |
jns folder_skip_sector |
push cx |
push es di |
push 0x8000 |
pop es |
xor bx, bx |
mov cx, 1 |
push es |
call [read_sectors] |
; copy data to the cache... |
pop ds |
pop di es |
cmp di, 0x2000 ; ...if there is free space, of course |
jae @f |
push si di |
mov cx, 0x100 |
xor si, si |
rep movsw |
mov di, es |
shr di, 8 |
add [ss:foldcache_size+di-0x92], 0x10 ; 0x10 new entries in the cache |
pop di si |
@@: |
push es |
push 0x8000 |
pop es |
push cs |
pop ds |
mov cx, 0x10 |
call [scan_for_filename] |
pop es |
pop cx |
jz lookup_done_pop |
folder_skip_sector: |
inc ax |
jnz @f |
inc dx |
@@: |
loop folder_next_sector |
pop ax ; ax = current cluster |
call get_next_cluster |
jc folder_next_cluster |
stc |
push ax |
lookup_done_pop: |
pop ax |
lookup_done: |
pop si |
pop ds |
; CF=1 <=> failed |
jnc found |
notfound: |
pop di |
mov bx, 2 ; file not found |
mov ax, 0xFFFF |
mov dx, ax ; invalid file size |
ret |
notfound_pop: |
pop ax |
jmp notfound |
found: |
mov ax, [es:di+26] ; get cluster |
test byte [es:di+11], 10h ; directory? |
jz regular_file |
cmp byte [si-1], 0 |
jz notfound ; don't read directories as a regular files |
; ok, we have found a directory and the caller requested a file into it |
pop di |
jmp parse_dir_loop ; restart with new cluster in ax |
regular_file: |
cmp byte [si-1], 0 |
jnz notfound ; file does not contain another files |
; ok, we have found a regular file and the caller requested it |
; save file size |
mov dx, [es:di+28] |
mov [filesize], dx |
mov dx, [es:di+30] |
mov [filesize+2], dx |
pop di |
mov si, [di+4] |
shl si, 3 |
push si ; [ds:di+4] = limit in 4K blocks |
les bx, [di] ; es:bx -> buffer |
clusloop: |
; ax = first cluster, top of stack contains limit in sectors |
mov si, ax ; remember current cluster |
xor cx, cx ; cx will contain number of consecutive clusters |
mov word [cur_delta], cx |
mov word [cur_delta+2], cx |
mov di, ax |
clusfind: |
inc di |
inc cx |
call get_next_cluster |
jnc clusread |
cmp ax, di |
jz clusfind |
stc |
clusread: |
pop di ; limit in sectors |
push ax ; save next cluster |
pushf ; save flags |
; read cx clusters, starting from si |
; calculate number of sectors |
xchg ax, cx |
mul [sect_per_clus] |
; dx:ax = number of sectors; compare with limit |
mov word [num_sectors], ax |
mov word [num_sectors+2], dx |
jmp @f |
continue_load_file: |
les bx, [di] ; es:bx -> buffer |
mov di, [di+4] ; ds:di = limit in 4K blocks |
shl di, 3 ; now di = limit in sectors |
mov ax, word [num_sectors] |
mov dx, word [num_sectors+2] |
mov si, [cur_cluster] |
push [next_cluster] |
push [flags] |
or ax, dx |
jz nextclus |
@@: |
test dx, dx |
jnz clusdecrease |
push dx ; limit was not exceeded |
cmp ax, di |
jbe @f |
pop ax |
clusdecrease: |
push 1 ; limit was exceeded |
mov ax, di |
@@: |
sub di, ax ; calculate new limit |
sub word [num_sectors], ax |
sbb word [num_sectors+2], 0 |
; calculate starting sector |
xchg ax, cx |
lea ax, [si-2] |
mul [sect_per_clus] |
add ax, word [cur_delta] |
adc dx, word [cur_delta+2] |
add word [cur_delta], cx |
adc word [cur_delta+2], 0 |
; read |
call [read_sectors2] |
pop dx |
; next cluster? |
nextclus: |
popf |
pop ax |
mov [cur_cluster], si |
mov [next_cluster], ax |
pushf |
pop [flags] |
jnc @f ; no next cluster => return |
mov dl, 1 ; dh=0 in any case |
test di, di |
jz @f ; if there is next cluster but current limit is 0 => return: limit exceeded |
push di |
jmp clusloop ; all is ok, continue |
hooked_err: |
mov sp, 7C00h-12-2 ; restore stack |
mov dx, 3 ; return: read error |
@@: |
mov bx, dx |
mov ax, [filesize] |
mov dx, [filesize+2] |
ret |
; Callback function for secondary loader |
callback: |
; in: ax = function number; only functions 1 and 2 are defined for now |
; save caller's stack |
mov dx, ss |
mov cx, sp |
; set our stack (required because we need ss=0) |
xor si, si |
mov ss, si |
mov sp, 7C00h-8 |
mov bp, 7C00h |
push dx |
push cx |
; call our function |
stc ; unsupported function |
dec ax |
jz callback_readfile |
dec ax |
jnz callback_ret |
; function 2: continue loading file |
; can be called only after function 1 returned value bx=1 (only part of file was loaded) |
; in: ds:di -> information structure |
; dw:dw address |
; dw limit in 4Kb blocks (0x1000 bytes) (must be non-zero and not greater than 0x100) |
; out: bx=0 - ok, bx=1 - still only part of file was loaded, bx=3 - read error |
; out: dx:ax = file size |
call continue_load_file |
jmp callback_ret_succ |
callback_readfile: |
; function 1: read file |
; in: ds:di -> information structure |
; dw:dw address |
; dw limit in 4Kb blocks (0x1000 bytes) (must be non-zero and not greater than 0x100) |
; ASCIIZ name |
; out: bx=0 - ok, bx=1 - file is too big, only part of file was loaded, bx=2 - file not found, bx=3 - read error |
; out: dx:ax = file size (0xFFFFFFFF if file was not found) |
call load_file |
callback_ret_succ: |
clc ; function is supported |
callback_ret: |
; restore caller's stack |
pop cx |
pop ss |
mov sp, cx |
; return to caller |
retf |
secondary_loader_info: |
dw 0, 0x1000 |
dw 0x30000 / 0x1000 |
db 'kord/loader',0 |
aKernelNotFound db 'Fatal error: cannot load the secondary loader',0 |
foldcache_clus dw 0,0,0,0,0,0,0 ; start with no folders in cache |
foldcache_mark rw 7 |
foldcache_size rw 7 |
filename rb 11 |
if $ > 0x8200 |
error: table overwritten |
end if |
/kernel/trunk/sec_loader/trunk/boot/fat1x/. |
---|
Property changes: |
Added: tsvn:logminsize |
+5 |
\ No newline at end of property |