multiboot.S
4.25 KB
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
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
/*
* Multiboot Option ROM
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, see <http://www.gnu.org/licenses/>.
*
* Copyright Novell Inc, 2009
* Authors: Alexander Graf <agraf@suse.de>
*/
#define NO_QEMU_PROTOS
#include "../../hw/fw_cfg.h"
#define BIOS_CFG_IOPORT_CFG 0x510
#define BIOS_CFG_IOPORT_DATA 0x511
#define MULTIBOOT_MAGIC 0x2badb002
/* Read a variable from the fw_cfg device.
Clobbers: %edx
Out: %eax */
.macro read_fw VAR
mov $\VAR, %ax
mov $BIOS_CFG_IOPORT_CFG, %dx
outw %ax, (%dx)
mov $BIOS_CFG_IOPORT_DATA, %dx
inb (%dx), %al
shl $8, %eax
inb (%dx), %al
shl $8, %eax
inb (%dx), %al
shl $8, %eax
inb (%dx), %al
bswap %eax
.endm
.code16
.text
.global _start
_start:
.short 0xaa55
.byte 1 /* (_end - _start) / 512 */
push %eax
push %ds
/* setup ds so we can access the IVT */
xor %ax, %ax
mov %ax, %ds
/* save old int 19 */
mov (0x19*4), %eax
mov %eax, %cs:old_int19
/* install our int 19 handler */
movw $int19_handler, (0x19*4)
mov %cs, (0x19*4+2)
pop %ds
pop %eax
lret
int19_handler:
/* DS = CS */
movw %cs, %ax
movw %ax, %ds
/* fall through */
run_multiboot:
cli
cld
mov %cs, %eax
shl $0x4, %eax
/* fix the gdt descriptor to be PC relative */
mov (gdt_desc+2), %ebx
add %eax, %ebx
mov %ebx, (gdt_desc+2)
/* fix the prot mode indirect jump to be PC relative */
mov (prot_jump), %ebx
add %eax, %ebx
mov %ebx, (prot_jump)
/* FS = bootinfo_struct */
read_fw FW_CFG_INITRD_ADDR
shr $4, %eax
mov %ax, %fs
/* ES = mmap_addr */
read_fw FW_CFG_INITRD_SIZE
shr $4, %eax
mov %ax, %es
/* Initialize multiboot mmap structs using int 0x15(e820) */
xor %ebx, %ebx
/* mmap start after first size */
movl $4, %edi
mmap_loop:
/* entry size (mmap struct) & max buffer size (int15) */
movl $20, %ecx
/* store entry size */
movl %ecx, %es:-4(%edi)
/* e820 */
movl $0x0000e820, %eax
/* 'SMAP' magic */
movl $0x534d4150, %edx
int $0x15
mmap_check_entry:
/* last entry? then we're done */
jb mmap_done
and %bx, %bx
jz mmap_done
/* valid entry, so let's loop on */
mmap_store_entry:
/* %ax = entry_number * 24 */
mov $24, %ax
mul %bx
mov %ax, %di
movw %di, %fs:0x2c
/* %di = 4 + (entry_number * 24) */
add $4, %di
jmp mmap_loop
mmap_done:
real_to_prot:
/* Load the GDT before going into protected mode */
lgdt:
data32 lgdt %cs:gdt_desc
/* get us to protected mode now */
movl $1, %eax
movl %eax, %cr0
/* the LJMP sets CS for us and gets us to 32-bit */
ljmp:
data32 ljmp *%cs:prot_jump
prot_mode:
.code32
/* initialize all other segments */
movl $0x10, %eax
movl %eax, %ss
movl %eax, %ds
movl %eax, %es
movl %eax, %fs
movl %eax, %gs
/* Jump off to the kernel */
read_fw FW_CFG_KERNEL_ADDR
mov %eax, %ecx
/* EBX contains a pointer to the bootinfo struct */
read_fw FW_CFG_INITRD_ADDR
movl %eax, %ebx
/* EAX has to contain the magic */
movl $MULTIBOOT_MAGIC, %eax
ljmp2:
jmp *%ecx
/* Variables */
.align 4, 0
old_int19: .long 0
prot_jump: .long prot_mode
.short 8
.align 4, 0
gdt:
/* 0x00 */
.byte 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
/* 0x08: code segment (base=0, limit=0xfffff, type=32bit code exec/read, DPL=0, 4k) */
.byte 0xff, 0xff, 0x00, 0x00, 0x00, 0x9a, 0xcf, 0x00
/* 0x10: data segment (base=0, limit=0xfffff, type=32bit data read/write, DPL=0, 4k) */
.byte 0xff, 0xff, 0x00, 0x00, 0x00, 0x92, 0xcf, 0x00
/* 0x18: code segment (base=0, limit=0x0ffff, type=16bit code exec/read/conf, DPL=0, 1b) */
.byte 0xff, 0xff, 0x00, 0x00, 0x00, 0x9e, 0x00, 0x00
/* 0x20: data segment (base=0, limit=0x0ffff, type=16bit data read/write, DPL=0, 1b) */
.byte 0xff, 0xff, 0x00, 0x00, 0x00, 0x92, 0x00, 0x00
gdt_desc:
.short (5 * 8) - 1
.long gdt
.align 512, 0
_end: