| 0,0 → 1,183 |
|---|
| ; KolibriOS bootloader |
| ; bootsector for loading from FAT32 flash (or hard) drive |
| ; intended for use with mtldr_f file in root folder |
| ; this code has been written by diamond in 2005,2006,2007 specially for KolibriOS |
| |
| ; this code is loaded by BIOS to 0000:7C00 |
| org 0x7C00 |
| jmp @f |
| nop |
| ; times 57h db 0 |
| file 'bt2.dat':3,57h |
| @@: |
| xor eax, eax |
| mov ds, ax |
| mov ss, ax |
| mov sp, 7C00h |
| mov [boot_drive], dl |
| cld |
| sti |
| push 800h |
| pop es |
| movzx ebx, word [7C0Eh] ; reserved_sect |
| mov [fat_start], ebx |
| mov al, byte [7C10h] ; num_fats |
| mul dword [7C24h] ; sect_fat |
| add eax, ebx |
| ; cluster 2 begins from sector eax |
| movzx ebx, byte [7C0Dh] ; sects_per_clust |
| add bx, bx |
| sub eax, ebx |
| mov [data_start], eax |
| mov eax, [7C2Ch] ; root_cluster |
| and eax, 0FFFFFFFh |
| fat32_parse_dir: |
| xor bx, bx |
| mov di, bx |
| push eax |
| call read_cluster |
| movzx cx, byte [7C0Dh] ; sects_per_clust |
| shl cx, 4 ; *0x200/0x20 |
| scan_cluster: |
| cmp byte [es:di], 0 |
| jz file_not_found |
| push cx di |
| mov cx, 11 |
| mov si, mtldr_f |
| repz cmpsb |
| pop di cx |
| jz file_found |
| add di, 20h |
| loop scan_cluster |
| pop eax |
| call next_cluster |
| jnc file_not_found |
| jc fat32_parse_dir |
| file_found: |
| pop eax |
| mov ax, [es:di+14h] |
| and ax, 0FFFh |
| shl eax, 10h |
| mov ax, [es:di+1Ah] |
| ; eax contains first cluster |
| @@: |
| xor bx, bx |
| push eax |
| call read_cluster |
| mov ax, es |
| movzx cx, byte [7C0Dh] |
| shl cx, 5 |
| add ax, cx |
| mov es, ax |
| pop eax |
| call next_cluster |
| jc @b |
| jmp 0:8000h |
| |
| file_not_found: |
| mov si, file_not_found_msg |
| sayerr: |
| call out_string |
| jmp $ |
| |
| read_cluster: |
| ; in: eax = cluster, bx->buffer |
| movzx ecx, byte [7C0Dh] |
| mul ecx |
| add eax, [data_start] |
| |
| ; read procedure |
| ; in: eax = absolute sector |
| ; cx = number of sectors |
| ; es:bx -> buffer |
| read: |
| add eax, [7C1Ch] ; hidden sectors |
| push es |
| read_loop: |
| pushad |
| ; allocate disk address packet on the stack |
| ; qword +8: absolute block number |
| push 0 |
| push 0 ; dword +C is high dword |
| push eax ; dword +8 is low dword |
| ; dword +4: buffer address |
| push es ; word +6 is segment |
| push bx ; word +4 is offset |
| ; word +2: number of blocks, limited to 7Fh |
| sub cx, 7Fh |
| sbb ax, ax |
| and ax, cx |
| add ax, 7Fh |
| push ax |
| shl ax, 5 |
| mov cx, es |
| add cx, ax |
| mov es, cx |
| ; word +0: size of packet = 10h |
| push 10h |
| ; now pair ss:sp contain address of disk address packet |
| mov ax, 4200h |
| mov dl, [boot_drive] |
| mov si, sp |
| int 13h |
| mov si, disk_read_err |
| jc sayerr |
| popaw |
| popad |
| add eax, 7Fh |
| sub cx, 7Fh |
| ja read_loop |
| pop es |
| ret |
| |
| next_cluster: |
| push es |
| push ds |
| pop es |
| mov bx, 7E00h |
| ; sector is 200h bytes long, one entry in FAT occupies 4 bytes |
| ; => 80h entries in sector |
| push eax |
| shr eax, 7 ; div 80h |
| cmp eax, [fat_cur_sector] |
| jz @f |
| mov [fat_cur_sector], eax |
| add eax, [fat_start] |
| mov cx, 1 |
| call read |
| @@: |
| pop eax |
| and eax, 7Fh |
| mov eax, [7E00h+eax*4] |
| and eax, 0FFFFFFFh |
| cmp eax, 0FFFFFF7h |
| mov si, bad_cluster |
| jz sayerr |
| pop es |
| ret |
| |
| out_string: |
| lodsb |
| test al, al |
| jz .xxx |
| mov ah, 0Eh |
| mov bx, 7 |
| int 10h |
| jmp out_string |
| .xxx: ret |
| |
| file_not_found_msg db 'Cannot find file ' |
| mtldr_f db 'MTLD_F32 ' |
| db 13,10,0 |
| disk_read_err db 'Disk read error',13,10,0 |
| bad_cluster db 'Bad cluster',13,10,0 |
| fat_cur_sector dd -1 |
| |
| times (7DFEh - $) db 0 |
| db 55h, 0AAh |
| |
| virtual at 7A00h |
| fat_start dd ? |
| data_start dd ? |
| boot_drive db ? |
| end virtual |