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global start
extern kernel_boot
extern kernel_main
extern kernel_start
extern kernel_end
bits 32
; base, limit, access, flags
%macro gdt_entry 4
db %2 & 0xff
db (%2 >> 8) & 0xff
db %1 & 0xff
db (%1 >> 8) & 0xff
db (%1 >> 16) & 0xff
db %3
db ((%2 >> 16) & 0x0f) | (%4 << 4)
db (%1 >> 24) & 0xff
%endmacro
MAGIC equ 0xe85250d6
FLAGS equ 0
LENGTH equ mb_end - mb_start
CHECKSUM equ -(MAGIC + LENGTH)
VGABUF equ 0x000B8000
KRNMAP equ 0xC0000000
section .multiboot.data
align 8
mb_start:
dd MAGIC
dd FLAGS
dd LENGTH
dd CHECKSUM
dw 0
dw 0
dd 8
mb_end:
section .rodata
align 16
gdt_start:
gdt_entry 0, 0, 0, 0
gdt_entry 0, 0xFFFFF, 0x9A, 0xC
gdt_entry 0, 0xFFFFF, 0x92, 0xC
gdt_end:
gdt_descriptor:
dw gdt_end - gdt_start - 1
dd gdt_start
section .bootstrap_stack
align 16
stack_start:
resb 16384 ; 16 KiB
stack_end:
section .bss
align 4096
page_directory:
resb 4096
page_table1:
resb 4096
section .multiboot.text
align 8
start:
; push ebx
; call kernel_boot
; pop eax
mov edi, page_table1 - KRNMAP
mov esi, 0
mov ecx, 1023
paging_cmp:
cmp esi, kernel_start
jl paging_add
cmp esi, kernel_end - KRNMAP
jge paging_map
mov edx, esi
or edx, 0x003
mov [edi], edx
paging_add:
add esi, 4096
add edi, 4
loop paging_cmp
paging_map:
mov dword [page_table1 - KRNMAP + 1023 * 4], VGABUF | 0x003
mov dword [page_directory - KRNMAP + 0], page_table1 - KRNMAP + 0x003
mov dword [page_directory - KRNMAP + 768 * 4], page_table1 - KRNMAP + 0x003
mov ecx, page_directory - KRNMAP
mov cr3, ecx
mov ecx, cr0
or ecx, 0x80010000
mov cr0, ecx
lea ecx, load_gdt
jmp near ecx
section .text
align 8
load_gdt:
cli
lgdt [gdt_descriptor]
mov eax, cr0
or al, 1
mov cr0, eax
jmp 0x08:load_kernel
load_kernel:
mov dword [page_directory], 0
mov ecx, cr3
mov cr3, ecx
mov ax, 0x10
mov ds, ax
mov ss, ax
mov es, ax
mov fs, ax
mov gs, ax
mov esp, stack_end
mov ebp, stack_end
sti
call kernel_main
cli
halt:
hlt
jmp halt
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