Случайные символы печатаются в загрузчике - PullRequest
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Случайные символы печатаются в загрузчике

1 голос
/ 25 мая 2020

Кто-нибудь знает, что не так с этим кодом? Я использую VirtualBox для запуска этого, и когда он его запускает, он просто рассылает случайные символы, а затем экран очищается черным с курсором в некоторой случайной области. Что не так с тем, как я загрузил второй сектор?

boot.asm 

; 16 bit mode to use 2 byte align with 32 bit mode 4 byte aligned and 64 bit mode 8 byte aligned

%define NEW_LINE 0x0D, 0x0A

[BITS 16]
org 0x0000          ;IP= 0x0000, changes what everything is "offset from" to 0

section .text
    jmp 0x07c0:start     ; missing a - after 0x7c0 because each digit in hex is worth 4 bits
                    ; CS to7c0, IP = start

variables:
    align 2
    loadstr: db 'Loading Bootloader...', NEW_LINE
    align 2
    loadstr_len: dw 23

%include "bootloader_modules/vga.asm"    ; include BIOS VEGA functions
%include "bootloader_modules/drive.asm"  ; include BIOS drive write functions

start:
    align 2 
    mov ax, cs
    mov es, ax
    mov ds, ax

    bios_set_video_mode WIDE_TEXT_MODE
    bios_print_string loadstr, loadstr_len, 0, 0, 0, BLACK_COLOR | WHITE_COLOR
    bios_read_disk sector_2, HARD_DISK_DRIVE_N, 0, 2, 0, 1

    ;jmp $

    jmp 0x07c0:second_start

zero_fill times 510 - ($-$$) db 0x00
bootloader_signature: dw 0xAA55

second_start:

    bios_print_string disk_string, 12, 0, 0, 0, BLACK_COLOR | WHITE_COLOR

    jmp $

disk_string: db 'Hello There!',NEW_LINE
;times 512 - ($-second_start) db 0x00
sector_2: times 512 - ($-second_start) db 0x00

vga.asm : 

;16_BIT_COLOR_PALLETE
%define BLACK_COLOR             0x000000
%define BLUE_COLOR              0x000001
%define GREEN_COLOR             0x000002
%define CYAN_COLOR              0x000003
%define RED_COLOR               0x000004
%define MAGENTA_COLOR           0x000005
%define BROWN_COLOR             0x000006
%define GREY_COLOR              0x000007
%define DARK_GREY_COLOR         0x000008
%define LIGH_BLUE_COLOR         0x000009
%define LIGHT_GREEN_COLOR       0x00000A
%define LIGHT_CYAN_COLOR        0x00000B
%define LIGHT_RED_COLOR         0x00000C
%define LIGHT_MAGENTA_COLOR     0x00000D
%define YELLOW_COLOR            0x00000E
%define WHITE_COLOR             0x00000F

%define BLACK_COLOR_M             0x000000
%define BLUE_COLOR_M              0x0000A8
%define GREEN_COLOR_M             0x00A800
%define CYAN_COLOR_M              0x00A8A8
%define RED_COLOR_M               0xA80000
%define MAGENTA_COLOR_M           0xA800A8
%define ORANGE_COLOR_M            0xA85400
%define GREY_COLOR_M              0xA8A8A8
%define DARK_GREY_COLOR_M         0x545454
%define LIGH_BLUE_COLOR_M         0x5454FE
%define LIGHT_GREEN_COLOR_M       0x54FE54
%define LIGHT_CYAN_COLOR_M        0x54FEFE
%define BRIGHT_RED_COLOR_M        0xFE5454
%define BRIGHT_MAGENTA_COLOR_M    0xFE54FE
%define YELLOW_COLOR_M            0xFEFE54
%define WHITE_COLOR_M             0xFEFEFE

;VIDEO_MODES
%define SHORT_TEXT_MODE      0x01
%define SHORT_TEXT_MODE_C    0x02
%define WIDE_TEXT_MODE       0x03
%define WIDE_TEXT_MODE_C     0x04

%define GRAPHICAL_MODE              0x05
%define GRAPHICAL_MODE_C            0x13
;%define GRAPHICAL_MODE_SHORT       0x05
%define GRAPHICAL_MODE_SHORT_C      0x13
;%define GRAPHICAL_MODE_SHORT_MC    0x13
;%define GRAPHICAL_MODE_MC          0x00
;%define GRAPHICAL_MODE_WIDE        0x00
%define GRAPHICAL_MODE_WIDE_C       0x12
%define GRAPHICAL_MODE_WIDE_MC      0x11

%macro bios_set_video_mode 1

    mov ah, 0
    mov al, %1

    int 0x10

%endmacro

%macro bios_print_string 6

    mov bp, %1    ; [ES:BP] is far pointer string to write

    mov ah, 0x13  ; write string
    mov al, 0x01  ; update cursoer after writing
    mov bh, %3    ; page number
    mov bl, %6    ; color attributes
    mov cx, [%2]  ; number of characters in string
    mov dh, %4    ; row
    mov dl, %5    ; column

    int 0x10

%endmacro

drive.asm : 

%define HARD_DISK_DRIVE_N 0x80
%define FLOPPY_DISK_DRIVE_N 0x0
%define COMPACT_DISK_DRIVE_N 0xE0

%macro bios_read_disk 6

    mov bx, %1 ; buffer pointer, the offset

    mov ah, 0x02
    mov dl, %2 ; drive number, 80 for hard drives
    mov ch, %3 ; cylinder number
    mov cl, %4 ; sector number
    mov dh, %5 ; head number
    mov al, %6 ; sectors to read

    int 0x13

    jc .read_error

    bios_print_string DRIVE_READ_SUCCESS_MSG, DRIVE_READ_SUCCESS_MSG_len, 0, 0, 0, BLACK_COLOR | WHITE_COLOR

    .read_error:
    bios_print_string DRIVE_READ_ERROR_MSG, DRIVE_READ_ERROR_MSG_len, 0, 0, 0, BLACK_COLOR | WHITE_COLOR

%endmacro

DRIVE_READ_ERROR_MSG: db 'Error reading from drive, carry flag set', NEW_LINE
DRIVE_READ_ERROR_MSG_len: dw 41
DRIVE_READ_SUCCESS_MSG: db 'Suc', NEW_LINE
DRIVE_READ_SUCCESS_MSG_len: dw 5
...