Creating a simple OS to retrieve hardware information.

This is a guidance to create a simple OS in windows to retrieve hardware information using assembly language.

Prerequisites

I am going to use a little bit different approach in this by using WSL2 (Windows Subsystem for Linux 2) to build the OS. You can read more about it in here.

You have to install nasm and mkisofs in wsl2 to get started. Open up the wsl terminal and run these command.

To install nasm :-

sudo apt install nasm

To install mkisofs :-

sudo apt-get install mkisofs

Implementation

You can get the code for Alpha_OS from github.

File structure of the Alpha_OS

• programs/ — Source code for programs added to the disk image.
• source/ — Contains the entire OS source code.
• source/bootload/ — Source to generate BOOTLOAD.BIN, which is added to the disk image when building.
• source/features/ — Components of Bubble OS(keyboard and screen).
• source/kernel.asm — The core kernel source file, which pulls in other source files.

You can build the OS by running the following command in the root directory of the OS. You must run the command in WSL terminal.

sudo  bash  ./build-linux.sh

These are some defined strings.

 strmemory  db "Base Memory size: ", 0x00
 strsmallextended db "Extended memory between(1M - 16M): ", 0x00
 strbigextended  db      "Extended memory above 16M: ", 0x00
 strCPUVendor  db "CPU Vendor : ", 0x00
 strCPUdescription db "CPU description: ", 0x00
 strNotSupported  db "Not supported.", 0x00
 strhdnumber  db "Number of hard drives: ",0x00
 strserialportnumber db "Number of serial ports: ", 0x00
 strserialport1  db "Base I/O address for serial port 1 (communications port 1 - COM 1): ", 0x00
 strtotalmemory  db "Total memory: ", 0x00

Code for reading the base memory.

 push ax
 push dx
 
 int 0x12  ; call interrupt 12 to get base mem size
 mov dx,ax 
 mov [basemem] , ax
 call _print_dec  ; display the number in decimal
 mov al, 0x6b
        mov ah, 0x0E            ; BIOS teletype acts on 'K' 
        mov bh, 0x00
        mov bl, 0x07
        int 0x10
 
 pop dx
 pop ax

Code for reading the extended memory

call _display_endl
        mov si, strsmallextended
        mov al, 0x01
        int 0x21
 
 xor cx, cx  ; Clear CX
 xor dx, dx  ; clear DX
 mov ax, 0xE801
 int 0x15  ; call interrupt 15h
 mov dx, ax  ; save memory value in DX as the procedure argument
 mov [extmem1], ax
 call _print_dec  ; print the decimal value in DX
 mov al, 0x6b
        mov ah, 0x0E            ; BIOS teletype acts on 'K'
        mov bh, 0x00
        mov bl, 0x07
        int 0x10
 xor cx, cx  ; clear CX
        xor dx, dx  ; clear DX
        mov ax, 0xE801
        int 0x15  ; call interrupt 15h
 mov ax, dx  ; save memory value in AX for division
 xor dx, dx
 mov si , 16
 div si   ; divide AX value to get the number of MB
 mov dx, ax
 mov [extmem2], ax
 push dx   ; save dx value
 
 call _display_endl
        mov si, strbigextended
        mov al, 0x01
        int 0x21
 
 pop dx   ; retrieve DX for printing
 call _print_dec
 mov al, 0x4D
        mov ah, 0x0E            ; BIOS teletype acts on 'M'
        mov bh, 0x00
        mov bl, 0x07
        int 0x10
 
 call _display_endl
 mov si, strtotalmemory
 mov al, 0x01
 int 0x21; total memory = basemem + extmem1 + extmem2
 mov ax, [basemem] 
 add ax, [extmem1] ; ax = ax + extmem1
 shr ax, 10
 add ax, [extmem2] ; ax = ax + extmem2
 mov dx, ax
 call _print_dec
 mov al, 0x4D            
 mov ah, 0x0E            ; BIOS teletype acts on 'M'
 mov bh, 0x00
 mov bl, 0x07
 int 0x10

Code for CPU Information

call _display_endl
 mov si, strCPUVendor
 mov al, 0x01
 int 0x21
 mov eax, 0x00000000  ; set eax register to get the vendor
 cpuid    
 mov eax, ebx  ; prepare for string saving
 mov ebx, edx
 mov edx, 0x00
 mov si, strVendorID
 call _save_string
 mov si, strVendorID  ;print string
 mov al, 0x01
 int 0x21
 call _display_endl
 mov si, strCPUdescription
 mov al, 0x01
 int 0x21
 mov eax, 0x80000000  ; First check if CPU support this 
 cpuid
 cmp eax, 0x80000004
 jb _cpu_not_supported  ; if not supported jump to function end
 mov eax, 0x80000002  ; get first part of the brand
 mov si, strBrand
 cpuid
 call _save_string
 add si, 16
 mov eax, 0x80000003  ; get second part of the brand
 cpuid
 call _save_string
 add si, 16
 mov eax, 0x80000004  ; get third part of the brand
 cpuid
 call _save_stringmov si, strBrand  ; print the saved Brand string
 mov al, 0x01
 int 0x21
 jmp _hard_info

The number of hard drives

_hard_info:
 call _display_endl
 mov si, strhdnumber
        mov al, 0x01
        int 0x21
 mov ax,0040h             ; look at 0040:0075 for a number
 mov es,ax                ;
 mov dl,[es:0075h]        ; move the number into DL register
 add dl,30h  ; add 48 to get ASCII value            
 mov al, dl
        mov ah, 0x0E            ; BIOS teletype acts on character 
        mov bh, 0x00
        mov bl, 0x07
        int 0x10

About serial ports

_serial_ports:
 call _display_endl
 mov si, strserialportnumber
 mov al, 0x01
 int 0x21mov ax, [es:0x10]
 shr ax, 9
 and ax, 0x0007
 add al, 30h
 mov ah, 0x0E            ; BIOS teletype acts on character
 mov bh, 0x00
 mov bl, 0x07
 int 0x10; Reading base I/O addresses
 ;Base I/O address for serial port 1 (communications port 1 - COM 1)
 mov ax, [es:0000h] ; Read address for serial port 1
 cmp ax, 0
 je _end
 call _display_endl
 mov si, strserialport1
        mov al, 0x01
        int 0x21
 mov dx, ax
 call _print_dec

You can run the Alpha_OS in VirtualBox.