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
192
193
194
195
196
197
198
199
200
201
202
203
|
/* $NetBSD: dos_file.S,v 1.6 2009/11/21 11:52:57 dsl Exp $ */
/* extracted from Tor Egge's patches for NetBSD boot */
#include <machine/asm.h>
/*
# MSDOS call "INT 0x21 Function 0x3d" to open a file.
# Call with %ah = 0x3d
# %al = 0x0 (access and sharing modes)
# %ds:%dx = ASCIZ filename
# %cl = attribute mask of files to look for
*/
.globl _C_LABEL(doserrno)
_C_LABEL(doserrno): .long 1
ENTRY(dosopen)
.code32
pushl %ebp
movl %esp, %ebp
pushl %edx
pushl %ebx
pushl %esi
pushl %edi
movl 0x8(%ebp), %edx # File name.
call _C_LABEL(prot_to_real) # enter real mode
.code16
push %ds
movl %edx, %eax
shrl $4, %eax
mov %ds, %si
add %si, %ax
mov %ax, %ds
and $0xf, %dx
movb $0x3d, %ah # Open existing file.
movb $0x0 , %al # ro
sti
int $0x21
cli
pop %ds
jnc ok1
mov %ax, _C_LABEL(doserrno)
movl $-1, %edx
jmp err1
ok1:
movl $0,%edx
mov %ax, %dx
err1:
calll _C_LABEL(real_to_prot) # back to protected mode
.code32
movl %edx, %eax # return value in %eax
popl %edi
popl %esi
popl %ebx
popl %edx
popl %ebp
ret
ENTRY(dosread)
.code32
pushl %ebp
movl %esp, %ebp
pushl %ebx
pushl %ecx
pushl %edx
pushl %esi
pushl %edi
movl 0x8(%ebp), %ebx # File handle
movl 0xc(%ebp), %edx # Buffer.
movl 0x10(%ebp), %ecx # Bytes to read
call _C_LABEL(prot_to_real) # enter real mode
.code16
push %ds
movl %edx, %eax
shrl $4, %eax
mov %ds, %si
add %si, %ax
mov %ax, %ds
and $0xf, %dx
movb $0x3f, %ah # Read from file or device
sti
int $0x21
cli
pop %ds
jnc ok2
mov %ax, _C_LABEL(doserrno)
movl $-1, %edx
jmp err2
ok2:
movl $0,%edx
mov %ax, %dx
err2:
calll _C_LABEL(real_to_prot) # back to protected mode
.code32
movl %edx, %eax # return value in %eax
popl %edi
popl %esi
popl %edx
popl %ecx
popl %ebx
popl %ebp
ret
ENTRY(dosclose)
.code32
pushl %ebp
movl %esp, %ebp
pushl %ebx
pushl %esi
pushl %edi
movl 0x8(%ebp), %ebx # File handle
call _C_LABEL(prot_to_real) # enter real mode
.code16
movb $0x3e, %ah # Close file.
sti
int $0x21
cli
jnc ok3
mov %ax, _C_LABEL(doserrno)
movl $-1, %ebx
jmp err3
ok3:
movl $0, %ebx
err3:
calll _C_LABEL(real_to_prot) # back to protected mode
.code32
movl %ebx, %eax # return value in %eax
popl %edi
popl %esi
popl %ebx
popl %ebp
ret
ENTRY(dosseek)
.code32
pushl %ebp
movl %esp, %ebp
pushl %ebx
pushl %ecx
pushl %edx
pushl %esi
pushl %edi
movl 0x8(%ebp), %ebx # File handle
movl 0xc(%ebp), %ecx # Offset
movl 0x10(%ebp) , %edx # whence
call _C_LABEL(prot_to_real) # enter real mode
.code16
movb $0x42, %ah # Seek
movb %dl, %al # whence
mov %cx, %dx #offs lo
shrl $0x10, %ecx #offs hi
sti
int $0x21
cli
jnc ok4
mov %ax, _C_LABEL(doserrno)
movl $-1, %edx
jmp err4
ok4:
shll $0x10, %edx #new ofs hi
mov %ax, %dx #new ofs lo
err4:
calll _C_LABEL(real_to_prot) # back to protected mode
.code32
movl %edx, %eax # return value in %eax
popl %edi
popl %esi
popl %edx
popl %ecx
popl %ebx
popl %ebp
ret
|
