kolibrios/kernel/trunk/bootloader/extended_primary_loader/fat1x/kordldr.f1x.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.
;*****************************************************************************
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
readloop:
push ax
; buffer should not cross a 64K boundary
push bx
shr bx, 4
mov cx, es
add bx, cx
neg bx
and bh, 0xF
shr bx, 5
jnz @f
mov bl, 0x80
@@:
cmp ax, bx
jbe @f
xchg ax, bx
@@:
pop bx
xchg ax, cx
; calculate starting sector
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 ax
sub ax, cx
jnz readloop
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 'kernel.mnt',0
aKernelNotFound db 'Fatal error: cannot load the kernel',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