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|
; boot.asm - stage 1
[bits 16]
[org 0x7C00]
start:
xor ax, ax
mov ds, ax
mov es, ax
mov ss, ax
; clear screen by big scrollup
mov ah, 0x06 ; scrollup function
mov al, 0 ; al contains the n of lines to scroll (0 is clearall)
mov bh, 0x07 ; 'attribute byte' 0x07 is white on black
mov cx, 0x0000 ; upper-left corner
mov dx, 0x184F ; bottom-right corner
int 0x10 ; call
; set cursor position back to default
mov ah, 0x02 ; set cur pos function
; position parameters:
mov bh, 0x00 ; page number (0)
mov dh, 0x00 ; row
mov dl, 0x00 ; col
int 0x10 ; call
mov si, msg1 ; print msg1
call print_string
mov ah, 0x02 ; set cur pos function
; position parameters:
mov bh, 0x00 ; page number (0)
mov dh, 0x01 ; row
mov dl, 0x00 ; col
int 0x10 ; call
mov si, msg2 ; print msg2
call print_string
mov ah, 0x02 ; set cur pos function
; position parameters:
mov bh, 0x00 ; page number (0)
mov dh, 0x02 ; row
mov dl, 0x00 ; col
int 0x10 ; call
mov si, msg3
call print_string
mov ah, 0x02 ; set cur pos function
; position parameters:
mov bh, 0x00 ; page number (0)
mov dh, 0x03 ; row
mov dl, 0x00 ; col
int 0x10 ; call
load_stage2:
mov ax, 0x0000
mov es, ax
mov bx, 0x1000
; load stage2 from disk - first sector at 0x1000
mov bx, 0x1000 ; load address
mov dh, 0
mov ch, 0
mov cl, 2 ; sector 2
mov al, 20 ; sectors to read
mov ah, 0x02
int 0x13
jc halt
; GDT for protected mode
gdt_start:
dq 0
dq 0x00CF9A000000FFFF ; code
dq 0x00CF92000000FFFF ; data
gdt_end:
gdt_descriptor:
dw gdt_end - gdt_start -1
dd gdt_start
; enable protected mode cleanly and transfer to 32-bit stub
cli
lgdt [gdt_descriptor]
mov eax, cr0
or eax, 1
mov cr0, eax
; far jump reloads CS with selector 0x08 and enters protected mode
jmp 0x08:pm_entry
; 32-bit entry point
[bits 32]
pm_entry:
; reload data segment registers with data selector (0x10)
mov ax, 0x10
mov ds, ax
mov es, ax
mov fs, ax
mov gs, ax
mov ss, ax
mov esp, 0x90000 ; setup stack
mov eax, 0x1000 ; jump to linear address 0x1000 (which wloud be where s2.bin was loaded)
jmp eax
halt:
hlt
jmp halt
print_string:
lodsb
cmp al, 0
je .done
mov ah, 0x0E
int 0x10
jmp print_string
.done:
ret
msg1 db `mull_bootloader hath bespoken unto thee:\n`, 0
msg2 db `\"behold, \'O user! mull_kernel doth now commence its solemn journey!\"\n`, 0
msg3 db `trying to kernel kernel :3`, 0
times 510-($-$$) db 0
dw 0xAA55
|
