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[BITS 32]
; Declare constants for the multiboot header.
MBALIGN equ 1 << 0 ; align loaded modules on page boundaries
MEMINFO equ 1 << 1 ; provide memory map
MBFLAGS equ MBALIGN | MEMINFO ; this is the Multiboot 'flag' field
MAGIC equ 0x1BADB002 ; 'magic number' lets bootloader find the header
CHECKSUM equ -(MAGIC + MBFLAGS) ; checksum of above, to prove we are multiboot
; Declare a multiboot header that marks the program as a kernel. These are magic
; values that are documented in the multiboot standard. The bootloader will
; search for this signature in the first 8 KiB of the kernel file, aligned at a
; 32-bit boundary. The signature is in its own section so the header can be
; forced to be within the first 8 KiB of the kernel file.
section .multiboot
align 4
dd MAGIC
dd MBFLAGS
dd CHECKSUM
section .bootstrap
present equ 1 << 7
not_sys equ 1 << 4
exec equ 1 << 3
cd equ 1 << 2
rw equ 1 << 1
access equ 1 << 0
gran_4k equ 1 << 7
sz_32 equ 1 << 6
long_m equ 1 << 5
global gdt.ptr
gdt:
.null: equ $ - gdt
dq 0
.code: equ $ - gdt
dd 0xffff
db 0
db present | not_sys | exec | rw
db gran_4k | long_m | 0xf
db 0
.data: equ $ - gdt
dd 0xffff
db 0
db present | not_sys | rw
db gran_4k | sz_32 | 0xf
db 0
.ptr:
dw $ - gdt - 1
dq gdt
global bootstrap
bootstrap:
mov dword [multiboot_magic], eax
mov dword [multiboot_header], ebx
mov eax, cr0
and eax, ~(1 << 31)
mov cr0, eax
mov edi, pml4 ;0x1000
mov cr3, edi
xor eax, eax
mov ecx, 1024
rep stosd
mov edi, 0x2000
mov ecx, 4096
rep stosd
mov edi, cr3
mov dword [edi], 0x2003
mov edi, 0x2000
mov dword [edi], 0x3003
add edi, 0x1000
mov dword [edi], 0x4003
mov dword [edi + 8], 0x5003
add edi, 0x1000
mov ebx, 0x00000003
mov ecx, 512
.set_entry:
mov dword [edi], ebx
add ebx, 0x1000
add edi, 8
loop .set_entry
mov edi, 0x5000
mov ecx, 512
.set_entry_2:
mov dword [edi], ebx
add ebx, 0x1000
add edi, 8
loop .set_entry_2
mov eax, cr4
or eax, 1 << 5
mov cr4, eax
mov ecx, 0xc0000080
rdmsr
or eax, 1 << 8 | 1 << 0
wrmsr
mov eax, cr0
or eax, 1 << 31
mov cr0, eax
lgdt [gdt.ptr]
mov ax, gdt.data
mov ds, ax
mov es, ax
mov fs, ax
mov gs, ax
mov ss, ax
extern start
jmp gdt.code:start
global set_pml4
set_pml4:
mov ecx, 0xC000080
rdmsr
and eax, ~(1 << 8)
wrmsr
mov eax, cr0
and eax, ~(1 << 31)
mov cr0, eax
mov cr3, edi
mov ecx, 0xC000080
rdmsr
or eax, 1 << 8
wrmsr
mov eax, cr0
or eax, 1 << 31
mov cr0, eax
retf
section .data
align 16
global multiboot_header
multiboot_header: dq 0
global multiboot_magic
multiboot_magic: dq 0
section .bss
global pml4
align 4096
pml4: resq 512
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