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
|
/*
* linux/boot/head.S
*
* Copyright (C) 1991, 1992, 1993 Linus Torvalds
*/
/*
* head.S contains the 32-bit startup code.
*
* NOTE!!! Startup happens at absolute address 0x00001000, which is also where
* the page directory will exist. The startup code will be overwritten by
* the page directory. [According to comments etc elsewhere on a compressed
* kernel it will end up at 0x1000 + 1Mb I hope so as I assume this. - AC]
*
* Page 0 is deliberately kept safe, since System Management Mode code in
* laptops may need to access the BIOS data stored there. This is also
* useful for future device drivers that either access the BIOS via VM86
* mode.
*/
/*
* High loaded stuff by Hans Lermen & Werner Almesberger, Feb. 1996
*/
.text
#include <linux/linkage.h>
#include <asm/segment.h>
#include <asm/page.h>
#include <asm/boot.h>
#include <asm/asm-offsets.h>
.section ".text.head","ax",@progbits
ENTRY(startup_32)
cld
/* test KEEP_SEGMENTS flag to see if the bootloader is asking
* us to not reload segments */
testb $(1<<6), BP_loadflags(%esi)
jnz 1f
cli
movl $(__BOOT_DS),%eax
movl %eax,%ds
movl %eax,%es
movl %eax,%fs
movl %eax,%gs
movl %eax,%ss
1:
/* Calculate the delta between where we were compiled to run
* at and where we were actually loaded at. This can only be done
* with a short local call on x86. Nothing else will tell us what
* address we are running at. The reserved chunk of the real-mode
* data at 0x1e4 (defined as a scratch field) are used as the stack
* for this calculation. Only 4 bytes are needed.
*/
leal (0x1e4+4)(%esi), %esp
call 1f
1: popl %ebp
subl $1b, %ebp
/* %ebp contains the address we are loaded at by the boot loader and %ebx
* contains the address where we should move the kernel image temporarily
* for safe in-place decompression.
*/
#ifdef CONFIG_RELOCATABLE
movl %ebp, %ebx
addl $(CONFIG_PHYSICAL_ALIGN - 1), %ebx
andl $(~(CONFIG_PHYSICAL_ALIGN - 1)), %ebx
#else
movl $LOAD_PHYSICAL_ADDR, %ebx
#endif
/* Replace the compressed data size with the uncompressed size */
subl input_len(%ebp), %ebx
movl output_len(%ebp), %eax
addl %eax, %ebx
/* Add 8 bytes for every 32K input block */
shrl $12, %eax
addl %eax, %ebx
/* Add 32K + 18 bytes of extra slack */
addl $(32768 + 18), %ebx
/* Align on a 4K boundary */
addl $4095, %ebx
andl $~4095, %ebx
/* Copy the compressed kernel to the end of our buffer
* where decompression in place becomes safe.
*/
pushl %esi
leal _end(%ebp), %esi
leal _end(%ebx), %edi
movl $(_end - startup_32), %ecx
std
rep
movsb
cld
popl %esi
/* Compute the kernel start address.
*/
#ifdef CONFIG_RELOCATABLE
addl $(CONFIG_PHYSICAL_ALIGN - 1), %ebp
andl $(~(CONFIG_PHYSICAL_ALIGN - 1)), %ebp
#else
movl $LOAD_PHYSICAL_ADDR, %ebp
#endif
/*
* Jump to the relocated address.
*/
leal relocated(%ebx), %eax
jmp *%eax
ENDPROC(startup_32)
.section ".text"
relocated:
/*
* Clear BSS
*/
xorl %eax,%eax
leal _edata(%ebx),%edi
leal _end(%ebx), %ecx
subl %edi,%ecx
cld
rep
stosb
/*
* Setup the stack for the decompressor
*/
leal boot_stack_end(%ebx), %esp
/*
* Do the decompression, and jump to the new kernel..
*/
movl output_len(%ebx), %eax
pushl %eax
# push arguments for decompress_kernel:
pushl %ebp # output address
movl input_len(%ebx), %eax
pushl %eax # input_len
leal input_data(%ebx), %eax
pushl %eax # input_data
leal boot_heap(%ebx), %eax
pushl %eax # heap area
pushl %esi # real mode pointer
call decompress_kernel
addl $20, %esp
popl %ecx
#if CONFIG_RELOCATABLE
/* Find the address of the relocations.
*/
movl %ebp, %edi
addl %ecx, %edi
/* Calculate the delta between where vmlinux was compiled to run
* and where it was actually loaded.
*/
movl %ebp, %ebx
subl $LOAD_PHYSICAL_ADDR, %ebx
jz 2f /* Nothing to be done if loaded at compiled addr. */
/*
* Process relocations.
*/
1: subl $4, %edi
movl 0(%edi), %ecx
testl %ecx, %ecx
jz 2f
addl %ebx, -__PAGE_OFFSET(%ebx, %ecx)
jmp 1b
2:
#endif
/*
* Jump to the decompressed kernel.
*/
xorl %ebx,%ebx
jmp *%ebp
.bss
/* Stack and heap for uncompression */
.balign 4
boot_heap:
.fill BOOT_HEAP_SIZE, 1, 0
boot_stack:
.fill BOOT_STACK_SIZE, 1, 0
boot_stack_end:
|
