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
|
/*
* 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]
*
* In SMP mode we keep this page safe. Really we ought to shuffle things and
* put the trampoline here. - AC. An SMP trampoline enters with %cx holding
* the stack base.
*
* 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
#define __ASSEMBLY__
#include <linux/config.h>
#include <linux/linkage.h>
#include <asm/segment.h>
.globl startup_32
startup_32:
cld
cli
movl $(__KERNEL_DS),%eax
mov %ax,%ds
mov %ax,%es
mov %ax,%fs
mov %ax,%gs
#ifdef __SMP__
orw %bx,%bx # What state are we in BX=1 for SMP
# 0 for boot
jz 2f # Initial boot
/*
* We are trampolining an SMP processor
*/
mov %ax,%ss
xorl %eax,%eax # Back to 0
mov %cx,%ax # SP low 16 bits
movl %eax,%esp
pushl 0 # Clear NT
popfl
ljmp $(__KERNEL_CS), $0x100000 # Into C and sanity
2:
#endif
lss SYMBOL_NAME(stack_start),%esp
xorl %eax,%eax
1: incl %eax # check that A20 really IS enabled
movl %eax,0x000000 # loop forever if it isn't
cmpl %eax,0x100000
je 1b
/*
* Initialize eflags. Some BIOS's leave bits like NT set. This would
* confuse the debugger if this code is traced.
* XXX - best to initialize before switching to protected mode.
*/
pushl $0
popfl
/*
* Clear BSS
*/
xorl %eax,%eax
movl $ SYMBOL_NAME(_edata),%edi
movl $ SYMBOL_NAME(_end),%ecx
subl %edi,%ecx
cld
rep
stosb
/*
* Do the decompression, and jump to the new kernel..
*/
subl $16,%esp # place for structure on the stack
pushl %esp # address of structure as first arg
call SYMBOL_NAME(decompress_kernel)
orl %eax,%eax
jnz 3f
xorl %ebx,%ebx
ljmp $(__KERNEL_CS), $0x100000
/*
* We come here, if we were loaded high.
* We need to move the move-in-place routine down to 0x1000
* and then start it with the buffer addresses in registers,
* which we got from the stack.
*/
3:
movl $move_routine_start,%esi
movl $0x1000,%edi
movl $move_routine_end,%ecx
subl %esi,%ecx
cld
rep
movsb
popl %esi # discard the address
popl %esi # low_buffer_start
popl %ecx # lcount
popl %edx # high_buffer_start
popl %eax # hcount
movl $0x100000,%edi
cli # make sure we don't get interrupted
ljmp $(__KERNEL_CS), $0x1000 # and jump to the move routine
/*
* Routine (template) for moving the decompressed kernel in place,
* if we were high loaded. This _must_ PIC-code !
*/
move_routine_start:
rep
movsb
movl %edx,%esi
movl %eax,%ecx # NOTE: rep movsb won't move if %ecx == 0
rep
movsb
xorl %ebx,%ebx
/*
* Well, the kernel relies on %esp pointing into low mem,
* with the decompressor loaded high this is no longer true,
* so we set esp here.
*/
mov $0x90000,%esp
ljmp $(__KERNEL_CS), $0x100000
move_routine_end:
|
