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
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
|
# write-buffered: like 'write', but for a buffered-file
== code
# instruction effective address register displacement immediate
# . op subop mod rm32 base index scale r32
# . 1-3 bytes 3 bits 2 bits 3 bits 3 bits 3 bits 2 bits 2 bits 0/1/2/4 bytes 0/1/2/4 bytes
# main:
#? e8/call test-write-buffered/disp32
#? e8/call test-write-buffered-with-intermediate-flush/disp32
e8/call run-tests/disp32 # 'run-tests' is a function created automatically by SubX. It calls all functions that start with 'test-'.
# syscall(exit, Num-test-failures)
8b/copy 0/mod/indirect 5/rm32/.disp32 . . 3/r32/EBX Num-test-failures/disp32 # copy *Num-test-failures to EBX
b8/copy-to-EAX 1/imm32/exit
cd/syscall 0x80/imm8
write-buffered: # f : (address buffered-file), msg : (address array byte) -> <void>
# pseudocode:
# in = msg->data
# inend = &msg->data[msg->length]
# while in < inend
# if f->write >= f->length
# flush(f)
# clear-stream(f)
# f->data[f->write] = *in
# ++f->write
# ++in
#
# registers:
# ESI : in
# ECX : inend
# EDI : f
# EDX : f->length
# EBX : f->write (cached copy, need to keep in sync)
# EAX : temp
#
# . prolog
55/push-EBP
89/copy 3/mod/direct 5/rm32/EBP . . . 4/r32/ESP . . # copy ESP to EBP
# . save registers
50/push-EAX
51/push-ECX
52/push-EDX
53/push-EBX
56/push-ESI
57/push-EDI
# EAX = msg
8b/copy 1/mod/*+disp8 5/rm32/EBP . . 0/r32/EAX 0xc/disp8 . # copy *(EBP+12) to EAX
# in/ESI = msg->data
8d/copy-address 1/mod/*+disp8 0/rm32/EAX . . . 6/r32/ESI 4/disp8 . # copy EAX+4 to ESI
# inend/ECX = &msg->data[msg->length]
8b/copy 0/mod/indirect 0/rm32/EAX . . . 1/r32/ECX . . # copy *EAX to ECX
8d/copy-address 0/mod/indirect 4/rm32/sib 6/base/ESI 1/index/ECX . 1/r32/ECX . . # copy ESI+ECX to ECX
# EDI = f
8b/copy 1/mod/*+disp8 5/rm32/EBP . . 7/r32/EDI 8/disp8 . # copy *(EBP+8) to EDI
# EDX = f->length
8b/copy 1/mod/*+disp8 7/rm32/EDI . . . 2/r32/EDX 0xc/disp8 . # copy *(EDI+12) to EDX
# EBX = f->write
8b/copy 1/mod/*+disp8 7/rm32/EDI . . . 3/r32/EBX 4/disp8 . # copy *(EDI+4) to EBX
$write-buffered:loop:
# if (in >= inend) break
39/compare 3/mod/direct 6/rm32/ESI . . . 1/r32/ECX . . # compare ESI with ECX
7d/jump-if-greater-or-equal $write-buffered:loop-end/disp8
# if (f->write >= f->length) flush and clear f's stream
39/compare 3/mod/direct 3/rm32/EBX . . . 2/r32/EDX . . # compare EBX with EDX
7c/jump-if-lesser $write-buffered:to-stream/disp8
# . persist f->write
89/copy 1/mod/*+disp8 7/rm32/EDI . . . 3/r32/EBX 4/disp8 . # copy EBX to *(EDI+4)
# . flush(f)
# . . push args
57/push-EDI
# . . call
e8/call flush/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 4/imm32 # add to ESP
# . clear-stream(stream = f+4)
# . . push args
8d/copy-address 1/mod/*+disp8 7/rm32/EDI . . . 0/r32/EAX 4/disp8 . # copy EDI+4 to EAX
50/push-EAX
# . . call
e8/call clear-stream/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 4/imm32 # add to ESP
# . clear EBX (cached f->write)
31/xor 3/mod/direct 3/rm32/EBX . . . 3/r32/EBX . . # clear EBX
$write-buffered:to-stream:
# write to stream
# f->data[f->write] = *in
# . AL = *in
31/xor 3/mod/direct 0/rm32/EAX . . . 0/r32/EAX . . # clear EAX
8a/copy-byte 0/mod/indirect 6/rm32/ESI . . . 0/r32/AL . . # copy byte at *ESI to AL
# . f->data[f->write] = AL
88/copy-byte 1/mod/*+disp8 4/rm32/sib 7/base/EDI 3/index/EBX . 0/r32/AL 0x10/disp8 . # copy AL to *(EDI+EBX+16)
# ++f->write
43/increment-EBX
# ++in
46/increment-ESI
eb/jump $write-buffered:loop/disp8
$write-buffered:loop-end:
# persist necessary variables from registers
89/copy 1/mod/*+disp8 7/rm32/EDI . . . 3/r32/EBX 4/disp8 . # copy EBX to *(EDI+4)
$write-buffered:end:
# . restore registers
5f/pop-to-EDI
5e/pop-to-ESI
5b/pop-to-EBX
5a/pop-to-EDX
59/pop-to-ECX
58/pop-to-EAX
# . epilog
89/copy 3/mod/direct 4/rm32/ESP . . . 5/r32/EBP . . # copy EBP to ESP
5d/pop-to-EBP
c3/return
test-write-buffered:
# - check that write-buffered writes to the file
# setup
# . clear-stream(_test-stream)
# . . push args
68/push _test-stream/imm32
# . . call
e8/call clear-stream/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 4/imm32 # add to ESP
# . clear-stream(_test-buffered-file+4)
# . . push args
b8/copy-to-EAX _test-buffered-file/imm32
05/add-to-EAX 4/imm32
50/push-EAX
# . . call
e8/call clear-stream/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 4/imm32 # add to ESP
# write-buffered(_test-buffered-file, "Abc")
# . . push args
68/push "Abc"/imm32
68/push _test-buffered-file/imm32
# . . call
e8/call write-buffered/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add to ESP
# flush(_test-buffered-file)
# . . push args
68/push _test-buffered-file/imm32
# . . call
e8/call flush/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 4/imm32 # add to ESP
# check-ints-equal(*_test-stream->data, "Abc", msg)
# . . push args
68/push "F - test-write-buffered-single"/imm32
68/push 0x636241/imm32
# . . push *_test-stream->data
b8/copy-to-EAX _test-stream/imm32
ff 6/subop/push 1/mod/*+disp8 0/rm32/EAX . . . . 0xc/disp8 . # push *(EAX+12)
# . . call
e8/call check-ints-equal/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 0xc/imm32 # add to ESP
# . end
c3/return
test-write-buffered-with-intermediate-flush:
# - check that write-buffered flushes in the middle if its buffer fills up
# setup
# . clear-stream(_test-stream)
# . . push args
68/push _test-stream/imm32
# . . call
e8/call clear-stream/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 4/imm32 # add to ESP
# . clear-stream(_test-buffered-file+4)
# . . push args
b8/copy-to-EAX _test-buffered-file/imm32
05/add-to-EAX 4/imm32
50/push-EAX
# . . call
e8/call clear-stream/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 4/imm32 # add to ESP
# _test-stream can hold 8 bytes, but _test-buffered-file can hold only 6.
# Try to write 7 bytes.
# . write-buffered(_test-buffered-file, "Abcdefg")
# . . push args
68/push "Abcdefg"/imm32
68/push _test-buffered-file/imm32
# . . call
e8/call write-buffered/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add to ESP
# don't flush
# 6 bytes should still have gotten to _test-stream
# . check-ints-equal(*_test-stream->write, 6, msg)
# . . push args
68/push "F - test-write-buffered-with-intermediate-flush: flushed data"/imm32
68/push 6/imm32
# . . push *_test-stream->write
b8/copy-to-EAX _test-stream/imm32
ff 6/subop/push 0/mod/indirect 0/rm32/EAX . . . . . . # push *EAX
# . . call
e8/call check-ints-equal/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 0xc/imm32 # add to ESP
# and 1 byte should still be in _test-buffered-file
# . check-ints-equal(*_test-buffered-file>write, 1, msg)
# . . push args
68/push "F - test-write-buffered-with-intermediate-flush: unflushed bytes"/imm32
68/push 1/imm32
# . . push *_test-buffered-file->write
b8/copy-to-EAX _test-buffered-file/imm32
ff 6/subop/push 1/mod/*+disp8 0/rm32/EAX . . . . 4/disp8 . # push *(EAX+4)
# . . call
e8/call check-ints-equal/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 0xc/imm32 # add to ESP
# . end
c3/return
# . . vim:nowrap:textwidth=0
|