73 lines
1.1 KiB
NASM
73 lines
1.1 KiB
NASM
%define MAGIC 0x1BADB002
|
|
%define FLAGS 0x0
|
|
|
|
section .multiboot
|
|
dd MAGIC
|
|
dd FLAGS
|
|
dd -(MAGIC + FLAGS)
|
|
|
|
section .text
|
|
global _start
|
|
_start:
|
|
cli
|
|
|
|
; Check if EAX contains this magic value that our bootloader should've set
|
|
cmp eax, 0x2BADB002
|
|
jne halt
|
|
|
|
; Load GDT
|
|
lgdt [gdtp]
|
|
; Offset to kernel data descriptor
|
|
mov ax, 0x10
|
|
mov es, ax
|
|
mov ds, ax
|
|
mov fs, ax
|
|
mov gs, ax
|
|
mov ss, ax
|
|
; Offset to kernel code descriptor
|
|
jmp 0x8:.use_code_seg
|
|
.use_code_seg:
|
|
mov esp, stack_bottom
|
|
mov ebp, esp
|
|
push ebx
|
|
and esp, 0xfffffff0
|
|
extern kernel
|
|
call kernel
|
|
cli
|
|
halt:
|
|
hlt
|
|
jmp halt
|
|
|
|
section .data
|
|
; GDT for a flat memory layout
|
|
; We get access to all memory and can utilize paging
|
|
global gdt
|
|
gdt:
|
|
gdt_null:
|
|
dq 0
|
|
gdt_kern_code:
|
|
dw 0xffff
|
|
dw 0x0000
|
|
db 0x00
|
|
db 0b10011010
|
|
db 0b11001111
|
|
db 0x00
|
|
gdt_kern_data:
|
|
dw 0xffff
|
|
dw 0x0000
|
|
db 0x00
|
|
db 0b10010010
|
|
db 0b11001111
|
|
db 0x00
|
|
gdt_end:
|
|
|
|
gdtp:
|
|
dw gdt_end - gdt - 1
|
|
dd gdt
|
|
|
|
section .bss
|
|
align 16
|
|
stack_top:
|
|
resb 16384
|
|
stack_bottom:
|