OSDev.org

bits   16
org      0x7c00
jmp   main
times 0x0b-($-$$) db 0
%include "fat_boot_sector.asm"
%include "real_mode_floppy.asm"
%include "real_mode_print.asm"
%include "real_mode_fat_12.asm"
bsAdditional           DB "Quartz Bootsector", 0x0A, 0x0D, 0
bsErrorMsg             DD 0
bsErrorMsgB            DB "Boot file `/qloader` can not be found.", 0x0A, 0x0D, 0
dFile db "QLOADER    "
main: ;Start
    xchg bx, bx
    cli
    xor ax, ax
    mov ss, ax
    mov ds, ax
    mov es, ax
    mov fs, ax
    mov gs, ax
    mov sp, 0x7C00
    sti
    mov si, bsAdditional
    call print
    mov WORD [bufloc], 0x0150
    push 1
    push 32
    call ReadSectors

    mov ax, dFile
    mov WORD [FileName], ax
   mov WORD [bsErrorMsg], bsErrorMsgB
    call FindFile ; >>> Here it gets stuck
    xor ax, ax
    mov bx, ax
    mov cx, ax
    mov dx, ax
    jmp 0:0x8000
times 510-($-$$) db 0
dw 0xAA55

%ifndef FAT_12
%define FAT_12
FileDirSeg dw 0
FileDir dw 0x3900
DirEntryN dw 224
FileBuf dw 0x0800
FileName dw 0
FindFile:
    xor dx, dx
    mov si, WORD [FileDir] ;ds:si = 0:FileDir
    mov di, WORD [FileName];es:di = 0:(string location)
    mov ax, WORD [FileDirSeg]
    mov ds, ax
    findloop:
    mov cx, 11
    push si
    push di
    mov al, BYTE [si]
    test al, al
    jz nfound
    repz cmpsb
    jz found
    pop di
    pop si
    inc dx
    add si, 0x20
    cmp dx, [DirEntryN];TODO
    jnz findloop
    ;Not found
    nfound:
    xor ax, ax
    mov ds, ax
    mov si, [bsErrorMsg]
    call print
    cli
    hlt
    found:
    pop di
    pop si
    push ds
    xor ax, ax
    mov ds, ax
    mov WORD [bufloc], ax
    ;Entry is in DS:SI
    add si, 26 ;First sector
    pop ds
    mov ax, WORD [si] ;AX contains the sector
    xor cx, cx
    mov ds, cx
    LoadToMem:
    mov bx, ax
    add bx, 31
    push ax
    push bx
    push 1
    call ReadSectors ; >>> Here it gets stuck
    pop ax
    add WORD [bufloc], 0x20
    ;Now find the next sector.
    xor dx, dx
    mov cx, 2
    div cx
    test dx, dx
    jz even_entry
    ;odd entry
    mov dx, 3
    mul dx
    mov bx, ax
    mov ax, word [bx+0x1501]
    shr ax, 4
    cmp ax, 0xFF0
    jl LoadToMem
    jmp DoneLoad
    even_entry:
    mov dx, 3
    mul dx
    mov bx, ax
    mov ax, word [bx+0x1500]
    and ax, 0x0FFF
    cmp ax, 0xFF0
    jl LoadToMem
    DoneLoad:
    ret
%endif

%ifndef _floppy
%include "fat_boot_sector.asm"
%define _floppy
sector db 0
head db 0
track db 0
count db 0
bufloc dw 0x0050
stacktemp dw 0
;PROCEDURE
;Reads sectors. (Real Mode)
;Two entries for stack:
;1st - Sector count
;2st - First sector given in LBA
ReadSectors:
    pop ax
    mov WORD [stacktemp], ax
    pop ax
    mov BYTE [count], al
    pop ax
    xor dx, dx
    div WORD [bpbSectorsPerTrack]
    inc dl
    mov BYTE [sector], dl
    xor dx, dx
    div WORD [bpbHeadsPerCylinder]
    mov BYTE [head], dl
    mov BYTE [track], al ;LBA to CHS
    read_try:
    xor ah, ah
    xor dl, dl
    int 0x13 ;Reset
    jc read_try
    xor dl, dl
    mov bx, WORD [bufloc] ;Loading at bufloc:0
    push es
    mov es, bx
    xor bx, bx
    xor dx, dx
    mov ah, 0x02
    mov al, BYTE [count]
    mov ch, BYTE [track]
    mov cl, BYTE [sector]
    mov dh, BYTE [head]
    int 0x13 ; >>> Here it gets stuck
    jc read_try
    pop es
    push word [stacktemp]
    ret
%endif

    found:
    pop di
    pop si
    push ds
    xor ax, ax
    mov ds, ax
    mov WORD [bufloc], ax

    mov bx, WORD [bufloc] ;Loading at bufloc:0
    push es
    mov es, bx
    xor bx, bx
    xor dx, dx
    mov ah, 0x02
    mov al, BYTE [count]
    mov ch, BYTE [track]
    mov cl, BYTE [sector]
    mov dh, BYTE [head]
    int 0x13 ; >>> Here it gets stuck