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comparison cos/kernel/goto64.asm @ 9:92ace1ca50a8

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64 bits kernel without interrupts but with printf in C
author windel
date Sun, 13 Nov 2011 12:47:47 +0100
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children fcdae30b2782
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8:edd70006d3e4 9:92ace1ca50a8
1 ;#!/usr/bin/nasm
2
3 ;
4 ; See http://wiki.osdev.org/User:Stephanvanschaik/Setting_Up_Long_Mode
5 ; Loader assembly to load the 64 bits kernel just after this file.
6
7 ; Assume that we are loaded at 1M (0x100000)
8 ;org 0x100000 ; this only works with flat bin output, not with elf64 output.
9
10 bits 32 ; Start in 32 bits mode.
11 ; Multiboot header:
12 ; Settings for multiboot header
13 PAGE_ALIGN equ 1 << 0
14 MEM_INFO equ 1 << 1
15 KLUDGE equ 1 << 16
16 MAGIC equ 0x1BADB002
17 FLAGS equ PAGE_ALIGN | MEM_INFO | KLUDGE ; align and provide memory map
18 CHECKSUM equ -(MAGIC+FLAGS)
19
20 ; actual multiboot header:
21 align 4
22 MultiBootHeader:
23 dd MAGIC
24 dd FLAGS
25 dd CHECKSUM
26 ; item below are present if bit 16 is set in flags
27 dd MultiBootHeader ; physical address in file of header (will be 0x100000 if put at start)
28 dd 0x100000 ; load_addr: load address, the address to start loading
29 dd 0x0 ; load_end_addr: zero indicates to load whole file
30 dd 0x0 ; bss_end_addr: zero indicates no bss segment present
31 dd loader ; entry_addr: jump to here
32
33 ; GDT, three entries: one for code, one for data
34 GDT64:
35 .Null: equ $ - GDT64
36 dw 0
37 dw 0
38 db 0
39 db 0
40 db 0
41 db 0
42 .Code: equ $ - GDT64
43 dw 0
44 dw 0
45 db 0
46 db 10011000b ; access
47 db 00100000b ; granularity
48 db 0
49 .Data: equ $ - GDT64
50 dw 0
51 dw 0
52 db 0
53 db 10010000b ; access
54 db 00000000b ; granularity
55 db 0
56 .Pointer: ; GDT pointer
57 dw $ - GDT64 - 1 ; Limit
58 dq GDT64 ; Base
59
60 ; Start of loader code:
61 global loader
62 loader:
63
64 ; Prepare paging:
65 ; PML4T - 0x1000
66 ; PDPT - 0x2000
67 ; PDT - 0x3000
68 ; PT - 0x4000
69
70 ; Clear the tables:
71 mov edi, 0x1000
72 mov cr3, edi ; CR3 is the page table address!
73 xor eax, eax
74 mov ecx, 4096
75 rep stosd
76 mov edi, cr3 ; restore edi
77
78 mov DWORD [edi], 0x2003 ; present and readwrite, points to first PDPT
79 add edi, 0x1000
80 mov DWORD [edi], 0x3003 ; present and readwrite, points to first PDT
81 add edi, 0x1000
82 mov DWORD [edi], 0x4003 ; present and readwrite, points to first PT
83 add edi, 0x1000
84
85 ; identity map the first two megabytes:
86 mov ebx, 0x00000003
87 mov ecx, 512
88 ; Fill all PT entries at 0x4000
89 SetEntry:
90 mov DWORD [edi], ebx
91 add ebx, 0x1000
92 add edi, 8
93 loop SetEntry
94
95 ; Enable paging:
96 mov eax, cr4
97 or eax, 1 << 5 ; PAE-bit is bit 5
98 mov cr4, eax
99
100 ; Set LM-bit (Long Mode bit):
101 mov ecx, 0xC0000080
102 rdmsr
103 or eax, 0x100 ; Set bit 8 (LM-bit)
104 wrmsr
105
106 ; Enable paging:
107 mov eax, cr0
108 or eax, 0x80000000 ; Set bit 31 (PG-bit)
109 mov cr0, eax
110
111 ; Load the GDT:
112 lgdt [GDT64.Pointer]
113
114 ; Jump to 64 bits kernel:
115 jmp GDT64.Code:Realm64
116
117 bits 64
118
119 ; realm64
120 Realm64:
121
122 cli
123 mov ax, GDT64.Data
124 mov ds, ax
125 mov es, ax
126 mov fs, ax
127 mov gs, ax
128
129 ; Done!
130
131 ; Setup stack pointer:
132 mov rsp, stackEnd
133 ; Put a B upper left corner
134 mov al, 66 ; 'B'
135 mov [0xb8000], al
136
137 ; Jump to code that is glued after this file
138 jmp einde
139
140 align 16
141 dataEnd:
142 ; reserve bytes for stack:
143 stackBegin:
144 resb 1024
145 stackEnd:
146
147 einde:
148 XCHG BX, BX ; bochs breakpoint
149
150 # Call kernel:
151 extern kmain
152 call kmain
153 # Should we ever return, remain in endless loop:
154 cli
155 hang:
156 hlt
157 jmp hang
158