120 lines
4.2 KiB
NASM
120 lines
4.2 KiB
NASM
|
[bits 16] ; Set to 16-bit mode
|
||
|
|
[org 0x7C00] ; BIOS loads the bootloader at this address
|
||
|
|
|
||
|
|
; Define GDT
|
||
|
|
gdt_start:
|
||
|
|
dw 0x0000 ; Limit (low)
|
||
|
|
dw 0x0000 ; Base (low)
|
||
|
|
db 0x00 ; Base (mid)
|
||
|
|
db 0x9A ; Access byte: Present, ring 0, executable
|
||
|
|
db 0xCF ; Flags: Granularity, 32-bit
|
||
|
|
db 0x00 ; Base (high)
|
||
|
|
|
||
|
|
dw 0x0000 ; Limit (low)
|
||
|
|
dw 0x0000 ; Base (low)
|
||
|
|
db 0x00 ; Base (mid)
|
||
|
|
db 0x92 ; Access byte: Present, ring 0, writable
|
||
|
|
db 0xCF ; Flags: Granularity, 32-bit
|
||
|
|
db 0x00 ; Base (high)
|
||
|
|
|
||
|
|
gdt_descriptor:
|
||
|
|
dw gdt_end - gdt_start - 1 ; Limit
|
||
|
|
dd gdt_start ; Base address
|
||
|
|
|
||
|
|
gdt_end:
|
||
|
|
|
||
|
|
start:
|
||
|
|
cli ; Disable interrupts
|
||
|
|
lgdt [gdt_descriptor] ; Load GDT
|
||
|
|
mov eax, cr0 ; Read CR0 register
|
||
|
|
or eax, 1 ; Set PE bit (Protected Mode Enable)
|
||
|
|
mov cr0, eax ; Write back to CR0
|
||
|
|
|
||
|
|
jmp 0x08:protected_mode_entry ; Far jump to flush the pipeline
|
||
|
|
|
||
|
|
protected_mode_entry:
|
||
|
|
mov ax, 0 ; Set data segment to the new segment
|
||
|
|
mov ds, ax ; Load data segment register
|
||
|
|
mov es, ax ; Load extra segment register
|
||
|
|
mov fs, ax ; Load fs segment register
|
||
|
|
mov gs, ax ; Load gs segment register
|
||
|
|
|
||
|
|
call clear_screen ; Clear the screen
|
||
|
|
mov si, welcome_message
|
||
|
|
call print_string_protected
|
||
|
|
|
||
|
|
command_loop:
|
||
|
|
mov si, prompt_message
|
||
|
|
call print_string_protected
|
||
|
|
|
||
|
|
call read_input
|
||
|
|
|
||
|
|
cmp al, 'h' ; Check for 'h' command (help)
|
||
|
|
je print_help
|
||
|
|
cmp al, 'q' ; Check for 'q' command (quit)
|
||
|
|
je quit_terminal
|
||
|
|
cmp al, 'f' ; Check for 'f' command (heckerfetch)
|
||
|
|
je heckerfetch
|
||
|
|
|
||
|
|
mov si, unknown_command_message
|
||
|
|
call print_string_protected
|
||
|
|
jmp command_loop ; Repeat the command loop
|
||
|
|
|
||
|
|
print_help:
|
||
|
|
mov si, help_message
|
||
|
|
call print_string_protected
|
||
|
|
jmp command_loop ; Return to command loop
|
||
|
|
|
||
|
|
heckerfetch:
|
||
|
|
mov si, heckerfetch_message
|
||
|
|
call print_string_protected
|
||
|
|
jmp command_loop ; Return to command loop
|
||
|
|
|
||
|
|
quit_terminal:
|
||
|
|
mov si, goodbye_message
|
||
|
|
call print_string_protected
|
||
|
|
jmp hang ; Hang the system
|
||
|
|
|
||
|
|
; Function to read a character from keyboard input
|
||
|
|
read_input:
|
||
|
|
xor eax, eax ; Clear EAX for reading character input
|
||
|
|
int 0x16 ; Call BIOS interrupt to read a character into AL
|
||
|
|
ret ; Return with character in AL
|
||
|
|
|
||
|
|
; Function to print a string in protected mode using VGA text buffer
|
||
|
|
print_string_protected:
|
||
|
|
mov edi, 0xb8000 ; VGA text buffer address
|
||
|
|
.next_char:
|
||
|
|
lodsb ; Load byte at DS:SI into AL and increment SI
|
||
|
|
cmp al, 0 ; Check for null terminator
|
||
|
|
je .done ; If null, we are done
|
||
|
|
mov [edi], ax ; Write character and attribute (white on black)
|
||
|
|
add edi, 2 ; Move to next character cell
|
||
|
|
jmp .next_char ; Repeat for next character
|
||
|
|
.done:
|
||
|
|
ret ; Return from function
|
||
|
|
|
||
|
|
; Function to clear the screen in protected mode
|
||
|
|
clear_screen:
|
||
|
|
xor di, di ; Start from the beginning of the VGA buffer
|
||
|
|
mov cx, 80 * 25 ; Number of characters in a standard text mode screen
|
||
|
|
mov ax, 0x07 ; Attribute for white on black background
|
||
|
|
.fill_screen:
|
||
|
|
stosw ; Store word in [ES:DI] and increment DI by 2
|
||
|
|
loop .fill_screen ; Repeat until CX is zero
|
||
|
|
ret ; Return from function
|
||
|
|
|
||
|
|
; Data section for messages
|
||
|
|
welcome_message db 'Welcome to the HeckerOS!', 0
|
||
|
|
prompt_message db 'Enter command (h for help, q to quit, f for heckerfetch): ', 0
|
||
|
|
help_message db 'Available commands: h (help), q (quit), f (heckerfetch)', 0
|
||
|
|
unknown_command_message db 'Unknown command! Try again.', 0
|
||
|
|
goodbye_message db 'Goodbye!', 0
|
||
|
|
heckerfetch_message db 'OS: HeckerOS Beta, CPU: HeckerSoft Generic CPU 0GHZ', 'Host: HeckerSoft Unknown Host', 0
|
||
|
|
|
||
|
|
; Bootloader signature (must be present)
|
||
|
|
times 510 - ($ - $$) db 0 ; Fill the rest of the sector with zeros
|
||
|
|
dw 0xAA55 ; Boot signature
|
||
|
|
|
||
|
|
hang:
|
||
|
|
jmp hang ; Jump to hang indefinitely
|