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
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
|
# primitives for emitting traces to a 'trace' stream, and for tests to make assertions on its contents
#
# A trace stream looks like a regular stream:
# write : int # index at which writes go
# read : int # index that we've read until
# data : (array byte) # prefixed by length as usual
# In a real trace the data will be in a special segment set aside for the purpose.
#
# primitives for operating on traces:
# - initialize-trace-stream (update global variable)
# - trace: stream, string
# - die: stream (exit(1) if using real trace)
# - check-trace-contains: stream, string/line, string/message (scans only from stream's read pointer, prints message to stderr on failure, updates stream's read pointer)
# - scan-to-next-line: stream (advance read pointer past next newline)
#
# Traces are very fundamental, so many of the helpers we create here won't be
# used elsewhere; we'll switch to more bounds-checked variants. But here we get
# bounds-checking for free; we allocate a completely disjoint segment for trace
# data, and overflowing it will generate a page fault.
== data
# We'll save the address of the trace segment here.
Trace-stream:
0/imm32
# Fake trace-stream for tests.
# Also illustrates the layout of the real trace-stream (segment).
_test-trace-stream:
# current write index
0/imm32
# current read index
0/imm32
# length
8/imm32
# data
00 00 00 00 00 00 00 00 # 8 bytes
== 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
# Allocate a new segment for the trace stream, initialize its length, and save its address to Trace-stream.
# The Trace-stream segment will consist of variable-length lines separated by newlines (0x0a)
initialize-trace-stream:
# EAX = new-segment(0x1000)
# . . push args
68/push 0x1000/imm32/N
# . . call
e8/call new-segment/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 4/imm32 # add to ESP
# copy EAX to *Trace-stream
89/copy 0/mod/indirect 5/rm32/.disp32 . . 0/r32/EAX Trace-stream/disp32 # copy EAX to *Trace-stream
# Trace-stream->length = 0x1000/N - 12
c7 0/subop/copy 1/mod/*+disp8 0/rm32/EAX . . . . 8/disp8 0xff4/imm32 # copy 0xff4 to *(EAX+8)
c3/return
# Append a string to the given trace stream.
# Silently give up if it's already full. Or truncate the string if there isn't enough room.
trace: # t : (address trace-stream), line : string
# . 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
# EDI = t
8b/copy 1/mod/*+disp8 5/rm32/EBP . . 7/r32/EDI 8/disp8 . # copy *(EBP+8) to EDI
# ESI = line
8b/copy 1/mod/*+disp8 5/rm32/EBP . . 6/r32/ESI 0xc/disp8 . # copy *(EBP+12) to ESI
# ECX = t->write
8b/copy 0/mod/indirect 7/rm32/EDI . . . 1/r32/ECX . . # copy *EDI to ECX
# EDX = t->length
8b/copy 1/mod/*+disp8 7/rm32/EDI . . . 2/r32/EDX 8/disp8 . # copy *(EDI+8) to EDX
# EAX = _append-3(&t->data[t->write], &t->data[t->length], line)
# . . push line
56/push-ESI
# . . push &t->data[t->length]
8d/copy-address 1/mod/*+disp8 4/rm32/sib 7/base/EDI 2/index/EDX . 3/r32/EBX 0xc/disp8 . # copy EDI+EDX+12 to EBX
53/push-EBX
# . . push &t->data[t->write]
8d/copy-address 1/mod/*+disp8 4/rm32/sib 7/base/EDI 1/index/ECX . 3/r32/EBX 0xc/disp8 . # copy EDI+ECX+12 to EBX
53/push-EBX
# . . call
e8/call _append-3/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 0xc/imm32 # add to ESP
# if (EAX == 0) return
3d/compare-EAX-and 0/imm32
74/jump-if-equal $trace:end/disp8
# t->write += EAX
01/add 0/mod/indirect 7/rm32/EDI . . . 0/r32/EAX . . # add EAX to *EDI
# refresh ECX = t->write
8b/copy 0/mod/indirect 7/rm32/EDI . . . 1/r32/ECX . . # copy *EDI to ECX
# EAX = _append-3(&t->data[t->write], &t->data[t->length], line)
# . . push line
68/push Newline/imm32
# . . push &t->data[t->length]
8d/copy-address 1/mod/*+disp8 4/rm32/sib 7/base/EDI 2/index/EDX . 3/r32/EBX 0xc/disp8 . # copy EDI+EDX+12 to EBX
53/push-EBX
# . . push &t->data[t->write]
8d/copy-address 1/mod/*+disp8 4/rm32/sib 7/base/EDI 1/index/ECX . 3/r32/EBX 0xc/disp8 . # copy EDI+ECX+12 to EBX
53/push-EBX
# . . call
e8/call _append-3/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 0xc/imm32 # add to ESP
# t->write += EAX
01/add 0/mod/indirect 7/rm32/EDI . . . 0/r32/EAX . . # add EAX to *EDI
$trace: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
clear-trace-stream: # t : (address trace-stream)
# . 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
# EAX = t
8b/copy 1/mod/*+disp8 5/rm32/EBP . . 0/r32/EAX 8/disp8 . # copy *(EBP+8) to EAX
# ECX = t->length
8b/copy 1/mod/*+disp8 0/rm32/EAX . . . 1/r32/ECX 8/disp8 . # copy *(EAX+8) to ECX
# ECX = &t->data[t->length]
8d/copy-address 1/mod/*+disp8 4/rm32/sib 0/base/EAX 1/index/ECX . 1/r32/ECX 0xc/disp8 . # copy EAX+ECX+12 to ECX
# t->write = 0
c7 0/subop/copy 0/mod/direct 0/rm32/EAX . . . . . 0/imm32 # copy to *EAX
# t->read = 0
c7 0/subop/copy 1/mod/*+disp8 0/rm32/EAX . . . . 4/disp8 0/imm32 # copy to *(EAX+4)
# EAX = t->data
81 0/subop/add 3/mod/direct 0/rm32/EAX . . . . . 0xc/imm32 # add to EAX
$clear-trace-stream:loop:
# if (EAX >= ECX) break
39/compare 3/mod/direct 0/rm32/EAX . . . 1/r32/ECX . . # compare EAX with ECX
7d/jump-if-greater-or-equal $clear-trace-stream:end/disp8
# *EAX = 0
c7 0/subop/copy 0/mod/direct 0/rm32/EAX . . . . . 0/imm32 # copy to *EAX
# EAX += 4
81 0/subop/add 3/mod/direct 0/rm32/EAX . . . . . 4/imm32 # add to EAX
eb/jump $clear-trace-stream:loop/disp8
$clear-trace-stream:end:
# . restore registers
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
# - tests
test-trace-single:
# clear-trace-stream(_test-trace-stream)
# . . push args
68/push _test-trace-stream/imm32
# . . call
e8/call clear-trace-stream/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 4/imm32 # add to ESP
# trace(_test-trace-stream, "Ab")
# . . push args
68/push "Ab"/imm32
68/push _test-trace-stream/imm32
# . . call
e8/call trace/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add to ESP
# check-ints-equal(*_test-trace-stream->data, 41/A 62/b 0a/newline 00, msg)
# . . push args
68/push "F - test-trace-single"/imm32
68/push 0x0a6241/imm32/Ab-newline
# . . push *_test-trace-stream->data
b8/copy-to-EAX _test-trace-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-trace-appends:
# clear-trace-stream(_test-trace-stream)
# . . push args
68/push _test-trace-stream/imm32
# . . call
e8/call clear-trace-stream/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 4/imm32 # add to ESP
# trace(_test-trace-stream, "C")
# . . push args
68/push "C"/imm32
68/push _test-trace-stream/imm32
# . . call
e8/call trace/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add to ESP
# trace(_test-trace-stream, "D")
# . . push args
68/push "D"/imm32
68/push _test-trace-stream/imm32
# . . call
e8/call trace/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add to ESP
# check-ints-equal(*_test-trace-stream->data, 43/C 0a/newline 44/D 0a/newline, msg)
# . . push args
68/push "F - test-trace-appends"/imm32
68/push 0x0a440a43/imm32/C-newline-D-newline
# . . push *_test-trace-stream->data
b8/copy-to-EAX _test-trace-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-trace-empty-line:
# clear-trace-stream(_test-trace-stream)
# . . push args
68/push _test-trace-stream/imm32
# . . call
e8/call clear-trace-stream/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 4/imm32 # add to ESP
# trace(_test-trace-stream, "")
# . . push args
68/push ""/imm32
68/push _test-trace-stream/imm32
# . . call
e8/call trace/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add to ESP
# check-ints-equal(*_test-trace-stream->data, 0, msg)
# . . push args
68/push "F - test-trace-empty-line"/imm32
68/push 0/imm32
# . . push *_test-trace-stream->data
b8/copy-to-EAX _test-trace-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
# - helpers
# 3-argument variant of _append
_append-3: # out : address, outend : address, s : (array byte) -> num_bytes_appended/EAX
# . prolog
55/push-EBP
89/copy 3/mod/direct 5/rm32/EBP . . . 4/r32/ESP . . # copy ESP to EBP
# . save registers
51/push-ECX
# EAX = _append-4(out, outend, &s->data[0], &s->data[s->length])
# . . push &s->data[s->length]
8b/copy 1/mod/*+disp8 5/rm32/EBP . . 0/r32/EAX 0x10/disp8 . # copy *(EBP+16) to EAX
8b/copy 0/mod/indirect 0/rm32/EAX . . . 1/r32/ECX . . # copy *EAX to ECX
8d/copy-address 1/mod/*+disp8 4/rm32/sib 0/base/EAX 1/index/ECX . 1/r32/ECX 4/disp8 . # copy EAX+ECX+4 to ECX
51/push-ECX
# . . push &s->data[0]
8d/copy-address 1/mod/*+disp8 0/rm32/EAX . . . 1/r32/ECX 4/disp8 . # copy EAX+4 to ECX
51/push-ECX
# . . push outend
ff 6/subop/push 1/mod/*+disp8 5/rm32/EBP . . . . 0xc/disp8 . # push *(EBP+12)
# . . push out
ff 6/subop/push 1/mod/*+disp8 5/rm32/EBP . . . . 8/disp8 . # push *(EBP+8)
# . . call
e8/call _append-4/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 0x10/imm32 # add to ESP
$_append-3:end:
# . restore registers
59/pop-to-ECX
# . epilog
89/copy 3/mod/direct 4/rm32/ESP . . . 5/r32/EBP . . # copy EBP to ESP
5d/pop-to-EBP
c3/return
# 4-argument variant of _append
_append-4: # out : address, outend : address, in : address, inend : address -> num_bytes_appended/EAX
# . prolog
55/push-EBP
89/copy 3/mod/direct 5/rm32/EBP . . . 4/r32/ESP . . # copy ESP to EBP
# . save registers
51/push-ECX
52/push-EDX
53/push-EBX
56/push-ESI
57/push-EDI
# EAX/num_bytes_appended = 0
b8/copy-to-EAX 0/imm32
# EDI = out
8b/copy 1/mod/*+disp8 5/rm32/EBP . . . 7/r32/EDI 8/disp8 . # copy *(EBP+8) to EDI
# EDX = outend
8b/copy 1/mod/*+disp8 5/rm32/EBP . . . 2/r32/EDX 0xc/disp8 . # copy *(EBP+12) to EDX
# ESI = in
8b/copy 1/mod/*+disp8 5/rm32/EBP . . . 6/r32/ESI 0x10/disp8 . # copy *(EBP+16) to ESI
# ECX = inend
8b/copy 1/mod/*+disp8 5/rm32/EBP . . . 1/r32/ECX 0x14/disp8 . # copy *(EBP+20) to ECX
$_append-4: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 $_append-4:end/disp8
# if (out >= outend) abort # just to catch test failures fast
39/compare 3/mod/direct 7/rm32/EDI . . . 2/r32/EDX . . # compare EDI with EDX
7d/jump-if-greater-or-equal $_append-4:abort/disp8
# *out = *in
8a/copy-byte 0/mod/indirect 6/rm32/ESI . . . 3/r32/BL . . # copy byte at *ESI to BL
88/copy-byte 0/mod/indirect 7/rm32/EDI . . . 3/r32/BL . . # copy byte at BL to *EDI
# ++num_bytes_appended
40/increment-EAX
# ++in
46/increment-ESI
# ++out
47/increment-EDI
eb/jump $_append-4:loop/disp8
$_append-4:end:
# . restore registers
5f/pop-to-EDI
5e/pop-to-ESI
5b/pop-to-EBX
5a/pop-to-EDX
59/pop-to-ECX
# . epilog
89/copy 3/mod/direct 4/rm32/ESP . . . 5/r32/EBP . . # copy EBP to ESP
5d/pop-to-EBP
c3/return
$_append-4:abort:
# . _write(2/stderr, error)
# . . push args
68/push "stream overflow\n"/imm32
68/push 2/imm32/stderr
# . . call
e8/call _write/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add to ESP
# . syscall(exit, 1)
bb/copy-to-EBX 1/imm32
b8/copy-to-EAX 1/imm32/exit
cd/syscall 0x80/imm8
# never gets here
# . . vim:nowrap:textwidth=0
|