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format ELF64
extrn kmain
PML4_TABLE = 0x1000
E820_MMAP = 0xf000
MSR_EFER = 0xc0000080
include 'bios.inc'
include 'page.inc'
include 'segdesc.inc'
section '.boot' executable writeable
org 0x7c00
use16
jmp far 0x0000:@f ; ensure cs = 0x0000
@@:
xor ax, ax
mov ds, ax
mov es, ax
; put stack directly bellow bootloader
mov ss, ax
mov sp, $$
cld
mov [boot_disk], dl
bios_disk_read ($$+0x200), 0, 0, 2, 57, disk_error
bios_e820_mmap E820_MMAP, e820_error
bios_a20_enable
bios_vga_write_mode_3
page_table_init_real PML4_TABLE
; disable IRQs
mov al, 0xff
out 0xa1, al
out 0x21, al
lidt [dummy_idtr]
; enable PAE (1<<5) and PGE (1<<7)
mov eax, (1 shl 7) or (1 shl 5)
mov cr4, eax
; point cr3 at PML4
mov edx, edi
mov cr3, edx
; enable long mode
mov ecx, MSR_EFER
rdmsr
or eax, (1 shl 8)
wrmsr
; enable protected mode
mov ebx, cr0
or ebx, (1 shl 31) or (1 shl 0)
mov cr0, ebx
lgdt [gdtr]
jmp far (gdt.kcode-gdt):longmode
e820_error:
; change beginning of error message ("disk" -> "e820")
mov dword [errmsg], 0x30323865
disk_error:
mov si, errmsg
mov ah, 0x0e
jmp @f
.loop:
int 0x10
@@:
lodsb
test al, al
jnz .loop
; wait until keypress, then jump to reset vector (reboot)
xor ah, ah
int 0x16
jmp far 0xffff:0x0000
use64
longmode:
mov ax, (gdt.kdata-gdt)
mov ds, ax
mov es, ax
mov ss, ax
cli
; copy kernel to 0x100000
mov ecx, (57*0x200)/8
mov esi, 0x7e00
mov edi, 0x100000
rep movsq
xor eax, eax
xor ebx, ebx
xor ecx, ecx
xor edx, edx
xor edi, edi
xor esi, esi
; put stack at top of addressable memory
mov esp, 0x200000
mov ebp, esp
; manually encoded 'jmp rel32', fasm throws an 'invalid use of symbol'
; error when generating code for a jmp to an external symbol after
; setting code origin with 'org' directive or a 'virtual at X' block.
db 0xe9
dd kmain-$-4
align 4
dw 0
label gdtr fword
.limit dw (gdt.sizeof - 1)
.addr dd gdt
align 4
errmsg db "disk error: press any key to reboot",0
align 8
gdt:
.null dq 0
.kcode seg_desc 0, 0, (GDT_CODE_64 or SEG_PRIV0)
.kdata seg_desc 0, 0, (GDT_DATA_64 or SEG_PRIV0)
.ucode seg_desc 0, 0, (GDT_CODE_64 or SEG_PRIV3)
.udata seg_desc 0, 0, (GDT_DATA_64 or SEG_PRIV3)
.sizeof = $ - gdt
align 4
boot_disk db 0, 0
label dummy_idtr fword
.limit dw 0
.addr dd 0
if ($-$$) <= 510
db 510-($-$$) dup 0
else
display "ERR: boot sector image exceeds 512 bytes",10
assert ($-$$) <= 510
end if
db 0x55,0xaa
|
