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.section .bootstrap_stack, "aw", @nobits
stack_bottom:
.skip 16384
stack_top:
.section .bss, "aw", @nobits
.align 4096
page_directory:
.skip 4096
page_table1:
.skip 4096
page_table2:
.skip 4096
.set P, 1<<0
.set RW, 1<<1
.set FLAGS, P | RW
.set KERNEL_VM, 0xC0000000
.section .multiboot.text, "a"
.global _start
.type _start, @function
_start:
_start:
cli
mov $stack_top - KERNEL_VM, %esp
pushl %eax
pushl %ebx
movl $page_table1 - KERNEL_VM + FLAGS, page_directory - KERNEL_VM + 0 * 4
movl $page_table2 - KERNEL_VM + FLAGS, page_directory - KERNEL_VM + 1 * 4
movl $page_table1 - KERNEL_VM + FLAGS, page_directory - KERNEL_VM + 768 * 4
movl $page_table2 - KERNEL_VM + FLAGS, page_directory - KERNEL_VM + 769 * 4
mov $0, %ecx
not_done:
mov $0x1000, %eax
mul %ecx
orl $FLAGS, %eax
mov %eax, %edi
// page_table1[%ecx] = 0x1000 * %ecx | 0x3
mov $4, %eax
mul %ecx
add $page_table1 - KERNEL_VM, %eax
movl %edi, (%eax)
// page_table2[%ecx] = 0x1000 * %ecx | 0x3
mov $4, %eax
mul %ecx
add $1024 * 0x1000, %edi
add $page_table2 - KERNEL_VM, %eax
movl %edi, (%eax)
inc %ecx
cmp $1024, %ecx
je done
jmp not_done
done:
movl $(page_directory - KERNEL_VM), %ecx
movl %ecx, %cr3
movl %cr0, %ecx
orl $0x80001000, %ecx
movl %ecx, %cr0
lea 7f, %ecx
jmp *%ecx
.section .boot32.rodata
gdt:
gdt_null = . - gdt
.quad 0
kernel_code = . - gdt
.long 0xFFFF
.byte 0
.byte 0x9A
.byte 0xCF
.byte 0
kernel_data = . - gdt
.long 0xFFFF
.byte 0
.byte 0x92
.byte 0xCF
.byte 0
user_code = . - gdt
.long 0xFFFF
.byte 0
.byte 0xFA
.byte 0xCF
.byte 0
user_data = . - gdt
.long 0xFFFF
.byte 0
.byte 0xF2
.byte 0xCF
.byte 0
.global gdtp
gdtp:
.word . - gdt - 1
.long gdt
.section .text
7:
addl $KERNEL_VM, %esp
lgdtl gdtp
ljmp $0x08, $code
code:
movw $0x10, %ax
movw %ax, %ds
movw %ax, %es
movw %ax, %fs
movw %ax, %gs
movw %ax, %ss
call kernel_main
hlt
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