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
|
/* SPDX-License-Identifier: GPL-2.0+ */
/*
* U-Boot - x86 Startup Code
*
* (C) Copyright 2008-2011
* Graeme Russ, <graeme.russ@gmail.com>
*
* (C) Copyright 2002,2003
* Daniel Engström, Omicron Ceti AB, <daniel@omicron.se>
*/
#include <asm/global_data.h>
#include <asm/processor-flags.h>
#define BOOT_SEG 0xffff0000 /* linear segment of boot code */
#define a32 .byte 0x67;
#define o32 .byte 0x66;
.section .start16, "ax"
.code16
.globl start16
start16:
/* Save BIST */
movl %eax, %ecx
/* Set the Cold Boot / Hard Reset flag */
movl $GD_FLG_COLD_BOOT, %ebx
xorl %eax, %eax
movl %eax, %cr3 /* Invalidate TLB */
/* Turn off cache (this might require a 486-class CPU) */
movl %cr0, %eax
orl $(X86_CR0_NW | X86_CR0_CD), %eax
movl %eax, %cr0
wbinvd
/* load the temporary Global Descriptor Table */
o32 cs lidt idt_ptr
o32 cs lgdt gdt_ptr
/* Now, we enter protected mode */
movl %cr0, %eax
orl $X86_CR0_PE, %eax
movl %eax, %cr0
/* Flush the prefetch queue */
jmp ff
ff:
/* Finally restore BIST and jump to the 32-bit initialization code */
movw $code32start, %ax
movw %ax, %bp
movl %ecx, %eax
o32 cs ljmp *(%bp)
/* 48-bit far pointer */
code32start:
.long _start /* offset */
.word 0x10 /* segment */
idt_ptr:
.word 0 /* limit */
.long 0 /* base */
/*
* The following Global Descriptor Table is just enough to get us into
* 'Flat Protected Mode' - It will be discarded as soon as the final
* GDT is setup in a safe location in RAM
*/
gdt_ptr:
.word 0x1f /* limit (31 bytes = 4 GDT entries - 1) */
.long BOOT_SEG + gdt_rom /* base */
/* Some CPUs are picky about GDT alignment... */
.align 16
.globl gdt_rom
gdt_rom:
/*
* The GDT table ...
*
* Selector Type
* 0x00 NULL
* 0x08 Unused
* 0x10 32bit code
* 0x18 32bit data/stack
*/
/* The NULL Desciptor - Mandatory */
.word 0x0000 /* limit_low */
.word 0x0000 /* base_low */
.byte 0x00 /* base_middle */
.byte 0x00 /* access */
.byte 0x00 /* flags + limit_high */
.byte 0x00 /* base_high */
/* Unused Desciptor - (matches Linux) */
.word 0x0000 /* limit_low */
.word 0x0000 /* base_low */
.byte 0x00 /* base_middle */
.byte 0x00 /* access */
.byte 0x00 /* flags + limit_high */
.byte 0x00 /* base_high */
/*
* The Code Segment Descriptor:
* - Base = 0x00000000
* - Size = 4GB
* - Access = Present, Ring 0, Exec (Code), Readable
* - Flags = 4kB Granularity, 32-bit
*/
.word 0xffff /* limit_low */
.word 0x0000 /* base_low */
.byte 0x00 /* base_middle */
.byte 0x9b /* access */
.byte 0xcf /* flags + limit_high */
.byte 0x00 /* base_high */
/*
* The Data Segment Descriptor:
* - Base = 0x00000000
* - Size = 4GB
* - Access = Present, Ring 0, Non-Exec (Data), Writable
* - Flags = 4kB Granularity, 32-bit
*/
.word 0xffff /* limit_low */
.word 0x0000 /* base_low */
.byte 0x00 /* base_middle */
.byte 0x93 /* access */
.byte 0xcf /* flags + limit_high */
.byte 0x00 /* base_high */
|
