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
|
/*
* Linux Boot 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>
*
* Based on code in hw/pc.c.
*/
#include "optionrom.h"
#define BOOT_ROM_PRODUCT "Linux loader"
BOOT_ROM_START
run_linuxboot:
cli
cld
jmp copy_kernel
boot_kernel:
read_fw FW_CFG_SETUP_ADDR
mov %eax, %ebx
shr $4, %ebx
/* All segments contain real_addr */
mov %bx, %ds
mov %bx, %es
mov %bx, %fs
mov %bx, %gs
mov %bx, %ss
/* CX = CS we want to jump to */
add $0x20, %bx
mov %bx, %cx
/* SP = cmdline_addr-real_addr-16 */
read_fw FW_CFG_CMDLINE_ADDR
mov %eax, %ebx
read_fw FW_CFG_SETUP_ADDR
sub %eax, %ebx
sub $16, %ebx
mov %ebx, %esp
/* Build indirect lret descriptor */
pushw %cx /* CS */
xor %ax, %ax
pushw %ax /* IP = 0 */
/* Clear registers */
xor %eax, %eax
xor %ebx, %ebx
xor %ecx, %ecx
xor %edx, %edx
xor %edi, %edi
xor %ebp, %ebp
/* Jump to Linux */
lret
copy_kernel:
/* Read info block in low memory (0x10000 or 0x90000) */
read_fw FW_CFG_SETUP_ADDR
shr $4, %eax
mov %eax, %es
xor %edi, %edi
read_fw_blob_addr32_edi(FW_CFG_SETUP)
cmpw $0x203, %es:0x206 // if protocol >= 0x203
jae 1f // have initrd_max
movl $0x37ffffff, %es:0x22c // else assume 0x37ffffff
1:
/* Check if using kernel-specified initrd address */
read_fw FW_CFG_INITRD_ADDR
mov %eax, %edi // (load_kernel wants it in %edi)
read_fw FW_CFG_INITRD_SIZE // find end of initrd
add %edi, %eax
xor %es:0x22c, %eax // if it matches es:0x22c
and $-4096, %eax // (apart from padding for page)
jz load_kernel // then initrd is not at top
// of memory
/* pc.c placed the initrd at end of memory. Compute a better
* initrd address based on e801 data.
*/
mov $0xe801, %ax
xor %cx, %cx
xor %dx, %dx
int $0x15
/* Output could be in AX/BX or CX/DX */
or %cx, %cx
jnz 1f
or %dx, %dx
jnz 1f
mov %ax, %cx
mov %bx, %dx
1:
or %dx, %dx
jnz 2f
addw $1024, %cx /* add 1 MB */
movzwl %cx, %edi
shll $10, %edi /* convert to bytes */
jmp 3f
2:
addw $16777216 >> 16, %dx /* add 16 MB */
movzwl %dx, %edi
shll $16, %edi /* convert to bytes */
3:
read_fw FW_CFG_INITRD_SIZE
subl %eax, %edi
andl $-4096, %edi /* EDI = start of initrd */
movl %edi, %es:0x218 /* put it in the header */
load_kernel:
/* We need to load the kernel into memory we can't access in 16 bit
mode, so let's get into 32 bit mode, write the kernel and jump
back again. */
/* Reserve space on the stack for our GDT descriptor. */
mov %esp, %ebp
sub $16, %esp
/* Now create the GDT descriptor */
movw $((3 * 8) - 1), -16(%bp)
mov %cs, %eax
movzwl %ax, %eax
shl $4, %eax
addl $gdt, %eax
movl %eax, -14(%bp)
/* And load the GDT */
data32 lgdt -16(%bp)
mov %ebp, %esp
/* Get us to protected mode now */
mov $1, %eax
mov %eax, %cr0
/* So we can set ES to a 32-bit segment */
mov $0x10, %eax
mov %eax, %es
/* We're now running in 16-bit CS, but 32-bit ES! */
/* Load kernel and initrd */
read_fw_blob_addr32_edi(FW_CFG_INITRD)
read_fw_blob_addr32(FW_CFG_KERNEL)
read_fw_blob_addr32(FW_CFG_CMDLINE)
/* And now jump into Linux! */
mov $0, %eax
mov %eax, %cr0
/* ES = CS */
mov %cs, %ax
mov %ax, %es
jmp boot_kernel
/* Variables */
.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
BOOT_ROM_END
|
