Subversion Repositories Kolibri OS

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;;                                                              ;;

;; Copyright (C) KolibriOS team 2004-2015. All rights reserved. ;;

;; Distributed under terms of the GNU General Public License    ;;

;;                                                              ;;

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; 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

include "lang.inc"

lf              =     0ah

cr              =     0dh

pos_read_tmp    =     0700h                   ;position for temporary read

boot_program    =     07c00h                  ;position for boot code

seg_read_kernel =     01000h                  ;segment to kernel read

        jmp     start_program

        nop

; Boot Sector and BPB Structure

include 'floppy1440.inc'

;include 'floppy2880.inc'

;include 'floppy1680.inc'

;include 'floppy1743.inc'

start_program:

; 

        cld     ;clear direction flag for Phoenix BIOS, see next "lodsb"

        xor     ax, ax

        cli

        mov     ss, ax

        mov     sp, boot_program

        sti

; <\Efremenkov S.V.>

        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

        mov     [cluster1st+boot_program], bp   ; starting cluster of kernel file

        ; 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:

        mov     ax, 'KL'

        push    0

        pop     ds

        mov     si, loader_block+boot_program

        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

        jnz     .next

        cmp     ah, 02h                                 ; if read sectors

        jz      file_error_message

        mov     byte[write_err+boot_program], 1         ; if write sectors

        jmp     .ret

.next:

        push    ax bx cx dx

        int     13h

        pop     dx cx bx ax

        jc      newread

.ret:

        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

;------------------------------------------

if lang eq sp

loading         db      cr,lf,'Iniciando el sistema ',00h

else

loading         db      cr,lf,'Starting system ',00h

end if

error_message   db      13,10

kernel_name     db      'KERNEL  MNT ?',cr,lf,00h

FirstRootDirSecNum      dw      ?

RootDirSecs     dw      ?

data_start      dw      ?

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                       ; +0

                dw      0                       ; +1

                dw      write1st+boot_program   ; +3

                dw      0                       ; +5

write_err:      db      0                       ; +7

times   0x1fe-$ db 00h

        db      55h,0aah                        ;boot signature