1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
|
.intel_syntax noprefix
.code16
.extern _stack_start
.extern _stack_end
.global stage1_sector
.section .stage1, "ax"
stage1_sector:
xor ax, ax
mov ah, 0x0e
mov al, 'C'
mov bh, 0x0
mov bl, 0x0
int 0x10
cli
lgdt gdtr
mov eax, cr0
or eax, (1 << 0)
mov cr0, eax
jmp 0x8:_32_start
cli
hlt
.code32
_32_start:
mov eax, 0x10
mov ds, ax
mov ss, ax
mov es, ax
mov fs, ax
mov gs, ax
jmp 0x8:_32_entry
cli
hlt
_32_entry:
mov eax, offset _stack_start
mov ebp, eax
mov eax, offset _stack_end
mov esp, eax
call centry
cli
hlt
.code16
.section .stage1_ro, "aw"
gdt:
.quad 0x0 // Null seg
.word 0xFFFF // Code seg
.word 0x0000
.byte 0x0
.byte 0b10011011 // A=1 RW=1 DC=0 E=1 S=1 DPL=00 P=1
.byte 0b11001111
.byte 0x0000
.word 0xFFFF // Data Seg
.word 0x0000
.byte 0x0
.byte 0b10010011 // A=1 RW=1 DC=0 E=0 S=1 DPL=00 P=1
.byte 0b11001111
.byte 0x0000
end_gdt:
gdtr:
.word end_gdt - gdt - 1
.long gdt
|
