forked from KolibriOS/kolibrios
303 lines
7.1 KiB
NASM
303 lines
7.1 KiB
NASM
|
; FAT12 boot sector for Kolibri OS
|
||
|
|
;
|
||
|
|
; Copyright (C) Alex Nogueira Teixeira
|
||
|
|
; Copyright (C) Diamond
|
||
|
|
; Copyright (C) Dmitry Kartashov aka shurf
|
||
|
|
;
|
||
|
|
; Distributed under GPL, see file COPYING for details
|
||
|
|
;
|
||
|
|
; Version 1.0
|
||
|
|
|
||
|
|
lf equ 0ah
|
||
|
|
cr equ 0dh
|
||
|
|
|
||
|
|
pos_read_tmp equ 0700h ;position for temporary read
|
||
|
|
boot_program equ 07c00h ;position for boot code
|
||
|
|
seg_read_kernel equ 01000h ;segment to kernel read
|
||
|
|
|
||
|
|
jmp start_program
|
||
|
|
nop
|
||
|
|
|
||
|
|
; Boot Sector and BPB Structure
|
||
|
|
BS_OEMName db 'KOLIBRI ' ; db 8
|
||
|
|
BPB_BytsPerSec dw 512 ; bytes per sector
|
||
|
|
BPB_SecPerClus db 1 ; sectors per cluster
|
||
|
|
BPB_RsvdSecCnt dw 1 ; number of reserver sectors
|
||
|
|
BPB_NumFATs db 2 ; count of FAT data structures
|
||
|
|
BPB_RootEntCnt dw 224 ; count of 32-byte dir. entries (224*32 = 14 sectors)
|
||
|
|
BPB_TotSec16 dw 2880 ; count of sectors on the volume (2880 for 1.44 mbytes disk)
|
||
|
|
BPB_Media db 0f0h ; f0 - used for removable media
|
||
|
|
BPB_FATSz16 dw 9 ; count of sectors by one copy of FAT
|
||
|
|
BPB_SecPerTrk dw 18 ; sectors per track
|
||
|
|
BPB_NumHeads dw 2 ; number of heads
|
||
|
|
BPB_HiddSec dd 0 ; count of hidden sectors
|
||
|
|
BPB_TotSec32 dd 0 ; count of sectors on the volume (if > 65535)
|
||
|
|
BS_DrvNum db 0 ; int 13h drive number
|
||
|
|
BS_Reserved db 0 ; reserved
|
||
|
|
BS_BootSig db 29h ; Extended boot signature
|
||
|
|
BS_VolID dd 0 ; Volume serial number
|
||
|
|
BS_VolLab db 'KOLIBRI ' ; Volume label (db 11)
|
||
|
|
BS_FilSysType db 'FAT12 ' ; file system type (db 8)
|
||
|
|
|
||
|
|
start_program:
|
||
|
|
|
||
|
|
xor ax,ax
|
||
|
|
mov ss,ax
|
||
|
|
mov sp,boot_program
|
||
|
|
push ss
|
||
|
|
pop ds
|
||
|
|
|
||
|
|
; print loading string
|
||
|
|
mov si,loading+boot_program
|
||
|
|
loop_loading:
|
||
|
|
lodsb
|
||
|
|
or al,al
|
||
|
|
jz read_root_directory
|
||
|
|
mov ah,0eh
|
||
|
|
mov bx,7
|
||
|
|
int 10h
|
||
|
|
jmp loop_loading
|
||
|
|
|
||
|
|
read_root_directory:
|
||
|
|
push ss
|
||
|
|
pop es
|
||
|
|
|
||
|
|
; calculate some disk parameters
|
||
|
|
; - beginning sector of RootDir
|
||
|
|
mov ax,word [BPB_FATSz16+boot_program]
|
||
|
|
xor cx,cx
|
||
|
|
mov cl,byte [BPB_NumFATs+boot_program]
|
||
|
|
mul cx
|
||
|
|
add ax,word [BPB_RsvdSecCnt+boot_program]
|
||
|
|
mov word [FirstRootDirSecNum+boot_program],ax ; 19
|
||
|
|
mov si,ax
|
||
|
|
|
||
|
|
; - count of sectors in RootDir
|
||
|
|
mov bx,word [BPB_BytsPerSec+boot_program]
|
||
|
|
mov cl,5 ; divide ax by 32
|
||
|
|
shr bx,cl ; bx = directory entries per sector
|
||
|
|
mov ax,word [BPB_RootEntCnt+boot_program]
|
||
|
|
xor dx,dx
|
||
|
|
div bx
|
||
|
|
mov word [RootDirSecs+boot_program],ax ; 14
|
||
|
|
|
||
|
|
; - data start
|
||
|
|
add si,ax ; add beginning sector of RootDir and count sectors in RootDir
|
||
|
|
mov word [data_start+boot_program],si ; 33
|
||
|
|
; reading root directory
|
||
|
|
; al=count root dir sectrors !!!! TODO: al, max 255 sectors !!!!
|
||
|
|
mov ah,2 ; read
|
||
|
|
push ax
|
||
|
|
|
||
|
|
mov ax,word [FirstRootDirSecNum+boot_program]
|
||
|
|
call conv_abs_to_THS ; convert abs sector (AX) to BIOS T:H:S (track:head:sector)
|
||
|
|
pop ax
|
||
|
|
mov bx,pos_read_tmp ; es:bx read buffer
|
||
|
|
call read_sector
|
||
|
|
|
||
|
|
mov si,bx ; read buffer address: es:si
|
||
|
|
mov ax,[RootDirSecs+boot_program]
|
||
|
|
mul word [BPB_BytsPerSec+boot_program]
|
||
|
|
add ax,si ; AX = end of root dir. in buffer pos_read_tmp
|
||
|
|
|
||
|
|
; find kernel file in root directory
|
||
|
|
loop_find_dir_entry:
|
||
|
|
push si
|
||
|
|
mov cx,11
|
||
|
|
mov di,kernel_name+boot_program
|
||
|
|
rep cmpsb ; compare es:si and es:di, cx bytes long
|
||
|
|
pop si
|
||
|
|
je found_kernel_file
|
||
|
|
add si,32 ; next dir. entry
|
||
|
|
cmp si,ax ; end of directory
|
||
|
|
jb loop_find_dir_entry
|
||
|
|
|
||
|
|
file_error_message:
|
||
|
|
mov si,error_message+boot_program
|
||
|
|
|
||
|
|
loop_error_message:
|
||
|
|
lodsb
|
||
|
|
or al,al
|
||
|
|
jz freeze_pc
|
||
|
|
mov ah,0eh
|
||
|
|
mov bx,7
|
||
|
|
int 10h
|
||
|
|
jmp loop_error_message
|
||
|
|
|
||
|
|
freeze_pc:
|
||
|
|
jmp $ ; endless loop
|
||
|
|
|
||
|
|
; === KERNEL FOUND. LOADING... ===
|
||
|
|
|
||
|
|
found_kernel_file:
|
||
|
|
mov bp,[si+01ah] ; first cluster of kernel file
|
||
|
|
; <diamond>
|
||
|
|
mov [cluster1st+boot_program],bp ; starting cluster of kernel file
|
||
|
|
; <\diamond>
|
||
|
|
|
||
|
|
; reading first FAT table
|
||
|
|
mov ax,word [BPB_RsvdSecCnt+boot_program] ; begin first FAT abs sector number
|
||
|
|
call conv_abs_to_THS ; convert abs sector (AX) to BIOS T:H:S (track:head:sector)
|
||
|
|
mov bx,pos_read_tmp ; es:bx read position
|
||
|
|
mov ah,2 ; ah=2 (read)
|
||
|
|
mov al, byte [BPB_FATSz16+boot_program] ; FAT size in sectors (TODO: max 255 sectors)
|
||
|
|
call read_sector
|
||
|
|
jc file_error_message ; read error
|
||
|
|
|
||
|
|
mov ax,seg_read_kernel
|
||
|
|
mov es,ax
|
||
|
|
xor bx,bx ; es:bx = 1000h:0000h
|
||
|
|
|
||
|
|
|
||
|
|
; reading kernel file
|
||
|
|
loop_obtains_kernel_data:
|
||
|
|
; read one cluster of file
|
||
|
|
call obtain_cluster
|
||
|
|
jc file_error_message ; read error
|
||
|
|
|
||
|
|
; add one cluster length to segment:offset
|
||
|
|
push bx
|
||
|
|
mov bx,es
|
||
|
|
mov ax,word [BPB_BytsPerSec+boot_program] ;\
|
||
|
|
movsx cx,byte [BPB_SecPerClus+boot_program] ; | !!! TODO: !!!
|
||
|
|
mul cx ; | out this from loop !!!
|
||
|
|
shr ax,4 ;/
|
||
|
|
add bx,ax
|
||
|
|
mov es,bx
|
||
|
|
pop bx
|
||
|
|
|
||
|
|
mov di,bp
|
||
|
|
shr di,1
|
||
|
|
pushf
|
||
|
|
add di,bp ; di = bp * 1.5
|
||
|
|
add di,pos_read_tmp
|
||
|
|
mov ax,[di] ; read next entry from FAT-chain
|
||
|
|
popf
|
||
|
|
jc move_4_right
|
||
|
|
and ax,0fffh
|
||
|
|
jmp verify_end_sector
|
||
|
|
move_4_right:
|
||
|
|
mov cl,4
|
||
|
|
shr ax,cl
|
||
|
|
verify_end_sector:
|
||
|
|
cmp ax,0ff8h ; last cluster
|
||
|
|
jae execute_kernel
|
||
|
|
mov bp,ax
|
||
|
|
jmp loop_obtains_kernel_data
|
||
|
|
|
||
|
|
execute_kernel:
|
||
|
|
; <diamond>
|
||
|
|
mov ax,'KL'
|
||
|
|
push 0
|
||
|
|
pop ds
|
||
|
|
mov si,loader_block+boot_program
|
||
|
|
; </diamond>
|
||
|
|
push word seg_read_kernel
|
||
|
|
push word 0
|
||
|
|
retf ; jmp far 1000:0000
|
||
|
|
|
||
|
|
|
||
|
|
;------------------------------------------
|
||
|
|
; loading cluster from file to es:bx
|
||
|
|
obtain_cluster:
|
||
|
|
; bp - cluster number to read
|
||
|
|
; carry = 0 -> read OK
|
||
|
|
; carry = 1 -> read ERROR
|
||
|
|
|
||
|
|
; print one dot
|
||
|
|
push bx
|
||
|
|
mov ax,0e2eh ; ah=0eh (teletype), al='.'
|
||
|
|
xor bh,bh
|
||
|
|
int 10h
|
||
|
|
pop bx
|
||
|
|
|
||
|
|
writesec:
|
||
|
|
; convert cluster number to sector number
|
||
|
|
mov ax,bp ; data cluster to read
|
||
|
|
sub ax,2
|
||
|
|
xor dx,dx
|
||
|
|
mov dl,byte [BPB_SecPerClus+boot_program]
|
||
|
|
mul dx
|
||
|
|
add ax,word [data_start+boot_program]
|
||
|
|
|
||
|
|
call conv_abs_to_THS ; convert abs sector (AX) to BIOS T:H:S (track:head:sector)
|
||
|
|
patchhere:
|
||
|
|
mov ah,2 ; ah=2 (read)
|
||
|
|
mov al,byte [BPB_SecPerClus+boot_program] ; al=(one cluster)
|
||
|
|
call read_sector
|
||
|
|
retn
|
||
|
|
;------------------------------------------
|
||
|
|
|
||
|
|
;------------------------------------------
|
||
|
|
; read sector from disk
|
||
|
|
read_sector:
|
||
|
|
push bp
|
||
|
|
mov bp,20 ; try 20 times
|
||
|
|
newread:
|
||
|
|
dec bp
|
||
|
|
jz file_error_message
|
||
|
|
push ax bx cx dx
|
||
|
|
int 13h
|
||
|
|
pop dx cx bx ax
|
||
|
|
jc newread
|
||
|
|
pop bp
|
||
|
|
retn
|
||
|
|
;------------------------------------------
|
||
|
|
; convert abs. sector number (AX) to BIOS T:H:S
|
||
|
|
; sector number = (abs.sector%BPB_SecPerTrk)+1
|
||
|
|
; pre.track number = (abs.sector/BPB_SecPerTrk)
|
||
|
|
; head number = pre.track number%BPB_NumHeads
|
||
|
|
; track number = pre.track number/BPB_NumHeads
|
||
|
|
; Return: cl - sector number
|
||
|
|
; ch - track number
|
||
|
|
; dl - drive number (0 = a:)
|
||
|
|
; dh - head number
|
||
|
|
conv_abs_to_THS:
|
||
|
|
push bx
|
||
|
|
mov bx,word [BPB_SecPerTrk+boot_program]
|
||
|
|
xor dx,dx
|
||
|
|
div bx
|
||
|
|
inc dx
|
||
|
|
mov cl, dl ; cl = sector number
|
||
|
|
mov bx,word [BPB_NumHeads+boot_program]
|
||
|
|
xor dx,dx
|
||
|
|
div bx
|
||
|
|
; !!!!!!! ax = track number, dx = head number
|
||
|
|
mov ch,al ; ch=track number
|
||
|
|
xchg dh,dl ; dh=head number
|
||
|
|
mov dl,0 ; dl=0 (drive 0 (a:))
|
||
|
|
pop bx
|
||
|
|
retn
|
||
|
|
;------------------------------------------
|
||
|
|
|
||
|
|
loading db cr,lf,'Starting system ',00h
|
||
|
|
error_message db 13,10
|
||
|
|
kernel_name db 'KERNEL MNT ?',cr,lf,00h
|
||
|
|
FirstRootDirSecNum dw ?
|
||
|
|
RootDirSecs dw ?
|
||
|
|
data_start dw ?
|
||
|
|
|
||
|
|
; <diamond>
|
||
|
|
write1st:
|
||
|
|
push cs
|
||
|
|
pop ds
|
||
|
|
mov byte [patchhere+1+boot_program], 3 ; change ah=2 to ah=3
|
||
|
|
mov bp,[cluster1st+boot_program]
|
||
|
|
push 1000h
|
||
|
|
pop es
|
||
|
|
xor bx,bx
|
||
|
|
call writesec
|
||
|
|
mov byte [patchhere+1+boot_program], 2 ; change back ah=3 to ah=2
|
||
|
|
retf
|
||
|
|
cluster1st dw ?
|
||
|
|
loader_block:
|
||
|
|
db 1
|
||
|
|
dw 0
|
||
|
|
dw write1st+boot_program
|
||
|
|
dw 0
|
||
|
|
; <\diamond>
|
||
|
|
|
||
|
|
times 0x1fe-$ db 00h
|
||
|
|
|
||
|
|
db 55h,0aah ;boot signature
|