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
|
!
! setup.s is responsible for getting the system data from the BIOS,
! and putting them into the appropriate places in system memory.
! both setup.s and system has been loaded by the bootblock.
!
! 1-Jan-96 Modified by Chris Brady for use as a boot/loader for memtest-86.
#include "mtest.h"
.globl begtext, begdata, begbss, endtext, enddata, endbss
.text
begtext:
.data
begdata:
.bss
begbss:
.text
entry start
start:
! ok, the read went well so we get current cursor position and save it for
! posterity.
mov ax,#INITSEG ! this is done in bootsect already, but...
mov ds,ax
#ifdef APM
! check for APM BIOS
mov ax,#0x05300 ! APM BIOS installation check
xor bx,bx
int 0x15
jc done_apm_bios ! error -> no APM BIOS
cmp bx,#0x0504d ! check for "PM" signature
jne done_apm_bios ! no signature -> no APM BIOS
mov ax,#0x05304 ! Disconnect first just in case
xor bx,bx
int 0x15 ! ignore return code
mov ax,#0x05301 ! Real Mode connect
xor bx,bx
int 0x15
jc done_apm_bios ! error
mov ax,#0x05308 ! Disable APM
mov bx,#0x0ffff
xor cx,cx
int 0x15
done_apm_bios:
#endif
! now we want to move to protected mode ...
cli ! no interrupts allowed !
mov al,#0x80 ! disable NMI for the bootup sequence
out #0x70,al
! first we move the system to its rightful place
mov ax,#TESTSEG ! start of destination segment
mov bx,#TSTLOAD ! start of source segment
cld ! 'direction'=0, movs moves forward
do_move:
mov es,ax ! destination segment
add ax,#0x100
cmp ax,#TESTSEG+TSTSIZE
jz end_move
mov ds,bx ! source segment
add bx,#0x100
sub di,di
sub si,si
mov cx,#0x800
rep
movsw
jmp do_move
! then we load the segment descriptors
end_move:
push cs
pop ds
lidt idt_48 ! load idt with 0,0
lgdt gdt_48 ! load gdt with whatever appropriate
! that was painless, now we enable A20
call empty_8042
mov al,#0xD1 ! command write
out #0x64,al
call empty_8042
mov al,#0xDF ! A20 on
out #0x60,al
call empty_8042
! Note that the short jump isn't strictly needed, althought there are
! reasons why it might be a good idea. It won't hurt in any case.
!
mov ax,#0x0001 ! protected mode (PE) bit
lmsw ax ! This is it!
jmp flush_instr
flush_instr:
mov ax,#KERNEL_DS
mov ds,ax
mov ss,ax
mov ax,#0x0720
mov ebx,#0xb8000
mov ecx,#0xc0000
clrlp:
mov (ebx),ax
inc ebx
inc ebx
cmp ebx,ecx
jnz clrlp
! Clear whole shared variable area for mobos that don't set RAM to 0
mov ax,#0x0000
mov ebx,#TESTADR+TSTSIZE-0x400
mov ecx,#TESTADR+TSTSIZE
clrvar:
mov (ebx),ax
inc ebx
inc ebx
cmp ebx,ecx
jnz clrvar
jmpi TESTADR,KERNEL_CS ! jmp offset 2000 of segment 0x10 (cs)
! This routine checks that the keyboard command queue is empty
! (after emptying the output buffers)
!
! No timeout is used - if this hangs there is something wrong with
! the machine, and we probably couldn't proceed anyway.
empty_8042:
call delay
in al,#0x64 ! 8042 status port
test al,#1 ! output buffer?
jz no_output
call delay
in al,#0x60 ! read it
jmp empty_8042
no_output:
test al,#2 ! is input buffer full?
jnz empty_8042 ! yes - loop
ret
!
! Delay is needed after doing i/o
!
delay:
.word 0x00eb ! jmp $+2
ret
gdt:
.word 0,0,0,0 ! dummy
.word 0,0,0,0 ! unused
.word 0x7FFF ! limit 128mb
.word 0x0000 ! base address=0
.word 0x9A00 ! code read/exec
.word 0x00C0 ! granularity=4096, 386
.word 0x7FFF ! limit 128mb
.word 0x0000 ! base address=0
.word 0x9200 ! data read/write
.word 0x00C0 ! granularity=4096, 386
idt_48:
.word 0 ! idt limit=0
.word 0,0x3 ! idt base=0L
gdt_48:
.word 0x800 ! gdt limit=2048, 256 GDT entries
.word 512+gdt,0x9 ! gdt base = 0X9xxxx
.text
endtext:
.data
enddata:
.bss
endbss:
|
