about summary refs log tree commit diff stats
path: root/apps/handle.subx
blob: 8e0a7ec31f5c9f418561cc1b921965ccebd62a58 (plain) (blame)
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
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
# A sketch of Mu-style handles or kinda-safe pointers, that add a modicum of
# checking to dynamically allocated memory.
#
# This approach avoids using 'allocate' directly in favor of two primitives:
#   - 'new', which allocates some space (the 'payload'), stores the address
#     along with an opaque 'alloc id' in a 'handle', and prepends the same
#     alloc id to the payload.
#   - 'lookup', which checks that the alloc id at the start of a handle matches
#     the alloc id at the start of the payload before returning the address.
#
# Layout of a handle:
#   offset 0: alloc id
#   offset 4: address
#
# To run:
#   $ ./bootstrap translate init.linux 0*.subx apps/handle.subx -o apps/handle
#   $ ./bootstrap run apps/handle
# Expected result is a successful lookup followed by a hard abort:
#   lookup succeeded
#   lookup failed
# (This file is a prototype. The 'tests' in it aren't real; failures are
# expected.)

== 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

Entry:
    # initialize heap
    # . Heap = new-segment(Heap-size)
    # . . push args
    68/push  Heap/imm32
    ff          6/subop/push        0/mod/indirect  5/rm32/.disp32            .             .           .           Heap-size/disp32                  # push *Heap-size
    # . . call
    e8/call  new-segment/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp

    e8/call  run-tests/disp32  # 'run-tests' is a function created automatically by SubX. It calls all functions that start with 'test-'.
$handle-main:end:
    # 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

new:  # ad: (addr allocation-descriptor), n: int, out: (handle _)
    # . prologue
    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
    # ecx = n+4
    8b/copy                         1/mod/*+disp8   5/rm32/ebp    .           .             .           1/r32/ecx   0xc/disp8       .                 # copy *(ebp+12) to ecx
    81          0/subop/add         3/mod/direct    1/rm32/ecx    .           .             .           .           .               4/imm32           # add to ecx
    # var eax: (handle _) = allocate(ad, ecx)
    # . . push args
    51/push-ecx
    ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           8/disp8         .                 # push *(ebp+8)
    # . . call
    e8/call  allocate/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
    # edx = out
    8b/copy                         1/mod/*+disp8   5/rm32/ebp    .           .             .           2/r32/edx   0x10/disp8      .                 # copy *(ebp+16) to edx
    # out->address = eax
    89/copy                         1/mod/*+disp8   2/rm32/edx    .           .             .           0/r32/eax   4/disp8         .                 # copy eax to *(edx+4)
    # if (eax == 0) out->alloc_id = 0, return
    3d/compare-eax-and  0/imm32
    75/jump-if-!=  $new:continue/disp8
    c7          0/subop/copy        0/mod/indirect  2/rm32/edx    .           .             .           .           .               0/imm32           # copy to *edx
    eb/jump  $new:end/disp8
$new:continue:
    # otherwise:
    # ecx = *Next-alloc-id
    8b/copy                         0/mod/indirect  5/rm32/.disp32            .             .           1/r32/ecx   Next-alloc-id/disp32              # copy *Next-alloc-id to ecx
    # *eax = *Next-alloc-id/ecx
    89/copy                         0/mod/indirect  0/rm32/eax    .           .             .           1/r32/ecx   .               .                 # copy ecx to *eax
    # out->alloc_id = *Next-alloc-id
    89/copy                         0/mod/indirect  2/rm32/edx    .           .             .           1/r32/ecx   .               .                 # copy ecx to *edx
    # increment *Next-alloc-id
    ff          0/subop/increment   0/mod/indirect  5/rm32/.disp32            .             .           .           Next-alloc-id/disp32              # increment *Next-alloc-id
$new:end:
    # . restore registers
    5a/pop-to-edx
    59/pop-to-ecx
    58/pop-to-eax
    # . epilogue
    89/copy                         3/mod/direct    4/rm32/esp    .           .             .           5/r32/ebp   .               .                 # copy ebp to esp
    5d/pop-to-ebp
    c3/return

test-new:
    # . prologue
    55/push-ebp
    89/copy                         3/mod/direct    5/rm32/ebp    .           .             .           4/r32/esp   .               .                 # copy esp to ebp
    # var heap/edx: allocation-descriptor
    68/push  0/imm32/limit
    68/push  0/imm32/curr
    89/copy                         3/mod/direct    2/rm32/edx    .           .             .           4/r32/esp   .               .                 # copy esp to edx
    # heap = new-segment(512)
    # . . push args
    52/push-edx
    68/push  0x200/imm32
    # . . call
    e8/call  new-segment/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
    # *Next-alloc-id = 0x34
    c7          0/subop/copy        0/mod/indirect  5/rm32/.disp32            .             .           .     Next-alloc-id/disp32  0x34/imm32        # copy to *Next-alloc-id
    # var handle/ecx: handle
    68/push  0/imm32/address
    68/push  0/imm32/alloc-id
    89/copy                         3/mod/direct    1/rm32/ecx    .           .             .           4/r32/esp   .               .                 # copy esp to ecx
    # new(heap, 2, handle/ecx)
    # . . push args
    51/push-ecx
    68/push  2/imm32/size
    52/push-edx
    # . . call
    e8/call  new/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
    # check-ints-equal(handle->alloc_id, 0x34, msg)
    # . . push args
    68/push  "F - test-new: alloc id of handle"/imm32
    68/push  0x34/imm32
    ff          6/subop/push        0/mod/indirect  1/rm32/ecx    .           .             .           .           .               .                 # push *ecx
    # . . call
    e8/call  check-ints-equal/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
    # check-ints-equal(*handle->address, 0x34, msg)
    # . . push args
    68/push  "F - test-new: alloc id of payload"/imm32
    68/push  0x34/imm32
    8b/copy                         1/mod/*+disp8   1/rm32/ecx    .           .             .           2/r32/edx   4/disp8         .                 # copy *(ecx+4) to edx
    ff          6/subop/push        0/mod/indirect  2/rm32/edx    .           .             .           .           .               .                 # push *edx
    # . . call
    e8/call  check-ints-equal/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
    # check-ints-equal(*Next-alloc-id, 0x35)
    # . . push args
    68/push  "F - test-new: next alloc id"/imm32
    68/push  0x35/imm32
    ff          6/subop/push        0/mod/indirect  5/rm32/.disp32            .             .           .           Next-alloc-id/disp32              # copy to *Next-alloc-id
    # . . call
    e8/call  check-ints-equal/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
    # clean up
    # . *Next-alloc-id = 1
    c7          0/subop/copy        0/mod/indirect  5/rm32/.disp32            .             .           .     Next-alloc-id/disp32  1/imm32           # copy to *Next-alloc-id
    # . epilogue
    89/copy                         3/mod/direct    4/rm32/esp    .           .             .           5/r32/ebp   .               .                 # copy ebp to esp
    5d/pop-to-ebp
    c3/return

_pending-test-new-failure:
    # . prologue
    55/push-ebp
    89/copy                         3/mod/direct    5/rm32/ebp    .           .             .           4/r32/esp   .               .                 # copy esp to ebp
    # . *Next-alloc-id = 0x34
    c7          0/subop/copy        0/mod/indirect  5/rm32/.disp32            .             .           .           Next-alloc-id/disp32  0x34/imm32  # copy to *Next-alloc-id
    # define an allocation-descriptor with no space left
    # . var ad/eax: allocation-descriptor = {0x10, 0x10}
    68/push  0x10/imm32/limit
    68/push  0x10/imm32/curr
    89/copy                         3/mod/direct    0/rm32/eax    .           .             .           4/r32/esp   .               .                 # copy esp to eax
    # . var handle/ecx = {random, random}
    68/push  1234/imm32/address
    68/push  5678/imm32/alloc-id
    89/copy                         3/mod/direct    1/rm32/ecx    .           .             .           4/r32/esp   .               .                 # copy esp to ecx
    # try to allocate
    # . new(ad, 2, handle/ecx)
    # . . push args
    51/push-ecx
    68/push  2/imm32/size
    50/push-eax
    # . . call
    e8/call  new/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
    # handle should be cleared
    # . check-ints-equal(handle->alloc_id, 0, msg)
    # . . push args
    68/push  "F - test-new-failure: alloc id of handle"/imm32
    68/push  0/imm32
    ff          6/subop/push        0/mod/indirect  1/rm32/ecx    .           .             .           .           .               .                 # push *ecx
    # . . call
    e8/call  check-ints-equal/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
    # . check-ints-equal(handle->address, 0, msg)
    # . . push args
    68/push  "F - test-new-failure: address of handle"/imm32
    68/push  0/imm32
    ff          6/subop/push        1/mod/*+disp8   1/rm32/ecx    .           .             .           .           4/disp8         .                 # push *(ecx+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
    # Next-alloc-id should be unmodified
    # . check-ints-equal(*Next-alloc-id, 0x34)
    # . . push args
    68/push  "F - test-new-failure: next alloc id"/imm32
    68/push  0x34/imm32
    ff          6/subop/push        0/mod/indirect  5/rm32/.disp32            .             .           .           Next-alloc-id/disp32              # copy to *Next-alloc-id
    # . . call
    e8/call  check-ints-equal/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
    # clean up
    # . *Next-alloc-id = 1
    c7          0/subop/copy        0/mod/indirect  5/rm32/.disp32            .             .           .     Next-alloc-id/disp32  1/imm32           # copy to *Next-alloc-id
    # . epilogue
    89/copy                         3/mod/direct    4/rm32/esp    .           .             .           5/r32/ebp   .               .                 # copy ebp to esp
    5d/pop-to-ebp
    c3/return

lookup:  # h: (handle T) -> eax: (addr T)
    # . prologue
    55/push-ebp
    89/copy                         3/mod/direct    5/rm32/ebp    .           .             .           4/r32/esp   .               .                 # copy esp to ebp
    # - as a proof of concept for future inlining, uses no general-purpose registers besides the output (eax)
    # eax = handle
    8b/copy                         1/mod/*+disp8   5/rm32/ebp    .           .             .           0/r32/eax   8/disp8         .                 # copy *(ebp+8) to eax
    # - inline {
    # push handle->alloc_id
    ff          6/subop/push        0/mod/indirect  0/rm32/eax    .           .             .           .           .               .                 # push *eax
    # eax = handle->address (payload)
    8b/copy                         1/mod/*+disp8   0/rm32/eax    .           .             .           .           4/disp8         .                 # copy *(eax+4) to eax
    # push handle->address
    50/push-eax
    # eax = payload->alloc_id
    8b/copy                         0/mod/indirect  0/rm32/eax    .           .             .           .           .               .                 # copy *eax to eax
    # if (eax != handle->alloc_id) abort
    39/compare                      1/mod/*+disp8   4/rm32/sib    4/base/esp  4/index/none  .           0/r32/eax   4/disp8         .                 # compare *(esp+4) and eax
    75/jump-if-!=  $lookup:abort/disp8
    # eax = pop handle->address
    58/pop-to-eax
    # discard handle->alloc_id
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    # add 4
    05/add-to-eax  4/imm32
    # - }
    # - alternative consuming a second register {
#?     # ecx = handle->alloc_id
#?     8b/copy                         0/mod/indirect  0/rm32/eax    .           .             .           1/r32/ecx   .               .                 # copy *eax to ecx
#?     # eax = handle->address (payload)
#?     8b/copy                         1/mod/*+disp8   0/rm32/eax    .           .             .           0/r32/eax   4/disp8         .                 # copy *(eax+4) to eax
#?     # if (ecx != *eax) abort
#?     39/compare                      0/mod/indirect  0/rm32/eax    .           .             .           1/r32/ecx   .               .                 # compare *eax and ecx
#?     75/jump-if-!=  $lookup:abort/disp8
#?     # add 4 to eax
#?     05/add-to-eax  4/imm32
    # - }
    # . epilogue
    89/copy                         3/mod/direct    4/rm32/esp    .           .             .           5/r32/ebp   .               .                 # copy ebp to esp
    5d/pop-to-ebp
    c3/return

$lookup:abort:
    # . _write(2/stderr, msg)
    # . . push args
    68/push  "lookup failed\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/exit-status
    b8/copy-to-eax  1/imm32/exit
    cd/syscall  0x80/imm8

test-lookup-success:
    # . prologue
    55/push-ebp
    89/copy                         3/mod/direct    5/rm32/ebp    .           .             .           4/r32/esp   .               .                 # copy esp to ebp
    # . save registers
    # var heap/ebx: allocation-descriptor
    68/push  0/imm32/limit
    68/push  0/imm32/curr
    89/copy                         3/mod/direct    3/rm32/ebx    .           .             .           4/r32/esp   .               .                 # copy esp to ebx
    # heap = new-segment(512)
    # . . push args
    53/push-ebx
    68/push  0x200/imm32
    # . . call
    e8/call  new-segment/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
    # var handle/ecx: handle
    68/push  0/imm32/address
    68/push  0/imm32/alloc-id
    89/copy                         3/mod/direct    1/rm32/ecx    .           .             .           4/r32/esp   .               .                 # copy esp to ecx
    # var old_top/edx = heap->curr
    8b/copy                         0/mod/indirect  3/rm32/ebx    .           .             .           2/r32/edx   .               .                 # copy *ebx to edx
    # new(heap, 2, handle)
    # . . push args
    51/push-ecx
    68/push  2/imm32/size
    53/push-ebx
    # . . call
    e8/call  new/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
    # eax = lookup(handle)
    # . . push args
    51/push-ecx
    # . . call
    e8/call  lookup/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    # eax contains old top of heap, except skipping the alloc id in the payload
    # . check-ints-equal(eax, old_top+4, msg)
    # . . push args
    68/push  "F - test-lookup-success"/imm32
    81          0/subop/add         3/mod/direct    2/rm32/edx    .           .             .           .           .               4/imm32           # add to edx
    52/push-edx
    50/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
    # clean up
    # . *Next-alloc-id = 1
    c7          0/subop/copy        0/mod/indirect  5/rm32/.disp32            .             .           .     Next-alloc-id/disp32  1/imm32           # copy to *Next-alloc-id
    # write(2/stderr, "lookup succeeded\n")
    # . . push args
    68/push  "lookup succeeded\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
    # . restore registers
    5a/pop-to-edx
    59/pop-to-ecx
    # . epilogue
    89/copy                         3/mod/direct    4/rm32/esp    .           .             .           5/r32/ebp   .               .                 # copy ebp to esp
    5d/pop-to-ebp
    c3/return

test-lookup-failure:
    # . prologue
    55/push-ebp
    89/copy                         3/mod/direct    5/rm32/ebp    .           .             .           4/r32/esp   .               .                 # copy esp to ebp
    # var heap/esi: allocation-descriptor
    68/push  0/imm32/limit
    68/push  0/imm32/curr
    89/copy                         3/mod/direct    6/rm32/esi    .           .             .           4/r32/esp   .               .                 # copy esp to esi
    # heap = new-segment(512)
    # . . push args
    56/push-esi
    68/push  0x200/imm32
    # . . call
    e8/call  new-segment/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
    # var h1/ecx: handle
    68/push  0/imm32/address
    68/push  0/imm32/alloc-id
    89/copy                         3/mod/direct    1/rm32/ecx    .           .             .           4/r32/esp   .               .                 # copy esp to ecx
    # var old_top/ebx = heap->curr
    8b/copy                         0/mod/indirect  6/rm32/esi    .           .             .           3/r32/ebx   .               .                 # copy *esi to ebx
    # first allocation, to h1
    # . new(heap, 2, h1)
    # . . push args
    51/push-ecx
    68/push  2/imm32/size
    56/push-esi
    # . . call
    e8/call  new/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
    # reset heap->curr to mimic reclamation
    89/copy                         0/mod/indirect  6/rm32/esi    .           .             .           3/r32/ebx   .               .                 # copy ebx to *esi
    # second allocation that returns the same address as the first
    # var h2/edx: handle
    68/push  0/imm32/address
    68/push  0/imm32/alloc-id
    89/copy                         3/mod/direct    2/rm32/edx    .           .             .           4/r32/esp   .               .                 # copy esp to edx
    # . new(heap, 2, h2)
    # . . push args
    52/push-edx
    68/push  2/imm32/size
    56/push-esi
    # . . call
    e8/call  new/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
    # check-ints-equal(h1->address, h2->address, msg)
    # . . push args
    68/push  "F - test-lookup-failure"/imm32
    ff          6/subop/push        1/mod/*+disp8   2/rm32/ecx    .           .             .           .           4/disp8         .                 # push *(edx+4)
    ff          6/subop/push        1/mod/*+disp8   1/rm32/ecx    .           .             .           .           4/disp8         .                 # push *(ecx+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
    # lookup(h1) should crash
    # . . push args
    51/push-ecx
    # . . call
    e8/call  lookup/disp32
    # should never get past this point
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    # clean up
    # . *Next-alloc-id = 1
    c7          0/subop/copy        0/mod/indirect  5/rm32/.disp32            .             .           .     Next-alloc-id/disp32  1/imm32           # copy to *Next-alloc-id
    # . epilogue
    89/copy                         3/mod/direct    4/rm32/esp    .           .             .           5/r32/ebp   .               .                 # copy ebp to esp
    5d/pop-to-ebp
    c3/return

== data

# Monotonically increasing counter for calls to 'new'
Next-alloc-id:  # int
    1/imm32

# . . vim:nowrap:textwidth=0