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starter.asm
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bits 16
extern kernel_main
extern interrupt_handler
extern scheduler
extern run_next_process
extern page_directory
global load_page_directory
global enable_paging
global dev_write
global dev_write_word
global dev_read
start:
mov ax, cs
mov ds, ax
call load_gdt
call init_video_mode
call enter_protected_mode
call setup_interrupts
call load_task_register
call 08h:start_kernel
load_gdt:
cli
lgdt [gdtr - start]
ret
setup_interrupts:
call remap_pic
call load_idt
ret
init_video_mode:
mov ah, 0h
mov al, 03h
int 10h
mov ah, 01h
mov cx, 2000h
int 10h
ret
enter_protected_mode:
mov eax, cr0
or eax, 1
mov cr0, eax
ret
remap_pic:
mov al, 11h
send_init_cmd_to_pic_master:
out 0x20, al
send_init_cmd_to_pic_slave:
out 0xa0, al
make_irq_starts_from_intr_32_in_pic_master:
mov al, 32d
out 0x21, al
make_irq_starts_from_intr_40_in_pic_slave:
mov al, 40d
out 0xa1, al
tell_pic_master_where_pic_slave_is_connected:
mov al, 04h
out 0x21, al
tell_pic_slave_where_pic_master_is_connected:
mov al, 02h
out 0xa1, al
mov al, 01h
tell_pic_master_the_arch_is_x86:
out 0x21, al
tell_pic_slave_the_arch_is_x86:
out 0xa1, al
mov al, 0h
make_pic_master_enables_all_irqs:
out 0x21, al
make_pic_slave_enables_all_irqs:
out 0xa1, al
ret
load_idt:
lidt [idtr - start]
ret
load_task_register:
mov ax, 40d
ltr ax
ret
bits 32
load_page_directory:
mov eax, [page_directory]
mov cr3, eax
ret
enable_paging:
mov eax, cr0
or eax, 80000000h
mov cr0, eax
ret
dev_write:
push edx
push eax
xor edx, edx
xor eax, eax
mov dx, [esp + 12]
mov al, [esp + 16]
out dx, al
pop eax,
pop edx
ret
dev_write_word:
push edx
push eax
xor edx, edx
xor eax, eax
mov dx, [esp + 12]
mov ax, [esp + 16]
out dx, ax
pop eax
pop edx
ret
dev_read:
push edx
xor edx, edx
xor eax, eax
mov dx, [esp + 8]
in ax, dx
pop edx
ret
start_kernel:
mov eax, 10h
mov ds, eax
mov ss, eax
mov es, eax
mov eax, 0h
mov fs, eax
mov gs, eax
sti
call kernel_main
%include "gdt.asm"
%include "idt.asm"
tss:
dd 0