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
|
/* -*- linux-c -*- ------------------------------------------------------- *
*
* Copyright (C) 1991, 1992 Linus Torvalds
* Copyright 2007 rPath, Inc. - All Rights Reserved
*
* This file is part of the Linux kernel, and is made available under
* the terms of the GNU General Public License version 2.
*
* ----------------------------------------------------------------------- */
/*
* arch/i386/boot/pm.c
*
* Prepare the machine for transition to protected mode.
*/
#include "boot.h"
#include <asm/segment.h>
/*
* Invoke the realmode switch hook if present; otherwise
* disable all interrupts.
*/
static void realmode_switch_hook(void)
{
if (boot_params.hdr.realmode_swtch) {
asm volatile("lcallw *%0"
: : "m" (boot_params.hdr.realmode_swtch)
: "eax", "ebx", "ecx", "edx");
} else {
asm volatile("cli");
outb(0x80, 0x70); /* Disable NMI */
io_delay();
}
}
/*
* A zImage kernel is loaded at 0x10000 but wants to run at 0x1000.
* A bzImage kernel is loaded and runs at 0x100000.
*/
static void move_kernel_around(void)
{
/* Note: rely on the compile-time option here rather than
the LOADED_HIGH flag. The Qemu kernel loader unconditionally
sets the loadflags to zero. */
#ifndef __BIG_KERNEL__
u16 dst_seg, src_seg;
u32 syssize;
dst_seg = 0x1000 >> 4;
src_seg = 0x10000 >> 4;
syssize = boot_params.hdr.syssize; /* Size in 16-byte paragraphs */
while (syssize) {
int paras = (syssize >= 0x1000) ? 0x1000 : syssize;
int dwords = paras << 2;
asm volatile("pushw %%es ; "
"pushw %%ds ; "
"movw %1,%%es ; "
"movw %2,%%ds ; "
"xorw %%di,%%di ; "
"xorw %%si,%%si ; "
"rep;movsl ; "
"popw %%ds ; "
"popw %%es"
: "+c" (dwords)
: "r" (dst_seg), "r" (src_seg)
: "esi", "edi");
syssize -= paras;
dst_seg += paras;
src_seg += paras;
}
#endif
}
/*
* Disable all interrupts at the legacy PIC.
*/
static void mask_all_interrupts(void)
{
outb(0xff, 0xa1); /* Mask all interrupts on the seconday PIC */
io_delay();
outb(0xfb, 0x21); /* Mask all but cascade on the primary PIC */
io_delay();
}
/*
* Reset IGNNE# if asserted in the FPU.
*/
static void reset_coprocessor(void)
{
outb(0, 0xf0);
io_delay();
outb(0, 0xf1);
io_delay();
}
/*
* Set up the GDT
*/
#define GDT_ENTRY(flags,base,limit) \
(((u64)(base & 0xff000000) << 32) | \
((u64)flags << 40) | \
((u64)(limit & 0x00ff0000) << 32) | \
((u64)(base & 0x00ffff00) << 16) | \
((u64)(limit & 0x0000ffff)))
struct gdt_ptr {
u16 len;
u32 ptr;
} __attribute__((packed));
static void setup_gdt(void)
{
/* There are machines which are known to not boot with the GDT
being 8-byte unaligned. Intel recommends 16 byte alignment. */
static const u64 boot_gdt[] __attribute__((aligned(16))) = {
/* CS: code, read/execute, 4 GB, base 0 */
[GDT_ENTRY_BOOT_CS] = GDT_ENTRY(0xc09b, 0, 0xfffff),
/* DS: data, read/write, 4 GB, base 0 */
[GDT_ENTRY_BOOT_DS] = GDT_ENTRY(0xc093, 0, 0xfffff),
};
struct gdt_ptr gdt;
gdt.len = sizeof(boot_gdt)-1;
gdt.ptr = (u32)&boot_gdt + (ds() << 4);
asm volatile("lgdtl %0" : : "m" (gdt));
}
/*
* Set up the IDT
*/
static void setup_idt(void)
{
static const struct gdt_ptr null_idt = {0, 0};
asm volatile("lidtl %0" : : "m" (null_idt));
}
/*
* Actual invocation sequence
*/
void go_to_protected_mode(void)
{
/* Hook before leaving real mode, also disables interrupts */
realmode_switch_hook();
/* Move the kernel/setup to their final resting places */
move_kernel_around();
/* Enable the A20 gate */
if (enable_a20()) {
puts("A20 gate not responding, unable to boot...\n");
die();
}
/* Reset coprocessor (IGNNE#) */
reset_coprocessor();
/* Mask all interrupts in the PIC */
mask_all_interrupts();
/* Actual transition to protected mode... */
setup_idt();
setup_gdt();
protected_mode_jump(boot_params.hdr.code32_start,
(u32)&boot_params + (ds() << 4));
}
|
