src/arm/decoder.c (view raw)
1/* Copyright (c) 2013-2014 Jeffrey Pfau
2 *
3 * This Source Code Form is subject to the terms of the Mozilla Public
4 * License, v. 2.0. If a copy of the MPL was not distributed with this
5 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
6#include <mgba/internal/arm/decoder.h>
7
8#include <mgba/internal/arm/decoder-inlines.h>
9
10#define ADVANCE(AMOUNT) \
11 if (AMOUNT > blen) { \
12 buffer[blen - 1] = '\0'; \
13 return total; \
14 } \
15 total += AMOUNT; \
16 buffer += AMOUNT; \
17 blen -= AMOUNT;
18
19static int _decodeRegister(int reg, char* buffer, int blen);
20static int _decodeRegisterList(int list, char* buffer, int blen);
21static int _decodePSR(int bits, char* buffer, int blen);
22static int _decodePCRelative(uint32_t address, uint32_t pc, char* buffer, int blen);
23static int _decodeMemory(struct ARMMemoryAccess memory, int pc, char* buffer, int blen);
24static int _decodeShift(union ARMOperand operand, bool reg, char* buffer, int blen);
25
26static const char* _armConditions[] = {
27 "eq",
28 "ne",
29 "cs",
30 "cc",
31 "mi",
32 "pl",
33 "vs",
34 "vc",
35 "hi",
36 "ls",
37 "ge",
38 "lt",
39 "gt",
40 "le",
41 "al",
42 "nv"
43};
44
45static int _decodeRegister(int reg, char* buffer, int blen) {
46 switch (reg) {
47 case ARM_SP:
48 strncpy(buffer, "sp", blen - 1);
49 return 2;
50 case ARM_LR:
51 strncpy(buffer, "lr", blen - 1);
52 return 2;
53 case ARM_PC:
54 strncpy(buffer, "pc", blen - 1);
55 return 2;
56 case ARM_CPSR:
57 strncpy(buffer, "cpsr", blen - 1);
58 return 4;
59 case ARM_SPSR:
60 strncpy(buffer, "spsr", blen - 1);
61 return 4;
62 default:
63 return snprintf(buffer, blen - 1, "r%i", reg);
64 }
65}
66
67static int _decodeRegisterList(int list, char* buffer, int blen) {
68 if (blen <= 0) {
69 return 0;
70 }
71 int total = 0;
72 strncpy(buffer, "{", blen - 1);
73 ADVANCE(1);
74 int i;
75 int start = -1;
76 int end = -1;
77 int written;
78 for (i = 0; i <= ARM_PC; ++i) {
79 if (list & 1) {
80 if (start < 0) {
81 start = i;
82 end = i;
83 } else if (end + 1 == i) {
84 end = i;
85 } else {
86 if (end > start) {
87 written = _decodeRegister(start, buffer, blen);
88 ADVANCE(written);
89 strncpy(buffer, "-", blen - 1);
90 ADVANCE(1);
91 }
92 written = _decodeRegister(end, buffer, blen);
93 ADVANCE(written);
94 strncpy(buffer, ",", blen - 1);
95 ADVANCE(1);
96 start = i;
97 end = i;
98 }
99 }
100 list >>= 1;
101 }
102 if (start >= 0) {
103 if (end > start) {
104 written = _decodeRegister(start, buffer, blen);
105 ADVANCE(written);
106 strncpy(buffer, "-", blen - 1);
107 ADVANCE(1);
108 }
109 written = _decodeRegister(end, buffer, blen);
110 ADVANCE(written);
111 }
112 strncpy(buffer, "}", blen - 1);
113 ADVANCE(1);
114 return total;
115}
116
117static int _decodePSR(int psrBits, char* buffer, int blen) {
118 if (!psrBits) {
119 return 0;
120 }
121 int total = 0;
122 strncpy(buffer, "_", blen - 1);
123 ADVANCE(1);
124 if (psrBits & ARM_PSR_C) {
125 strncpy(buffer, "c", blen - 1);
126 ADVANCE(1);
127 }
128 if (psrBits & ARM_PSR_X) {
129 strncpy(buffer, "x", blen - 1);
130 ADVANCE(1);
131 }
132 if (psrBits & ARM_PSR_S) {
133 strncpy(buffer, "s", blen - 1);
134 ADVANCE(1);
135 }
136 if (psrBits & ARM_PSR_F) {
137 strncpy(buffer, "f", blen - 1);
138 ADVANCE(1);
139 }
140 return total;
141}
142
143static int _decodePCRelative(uint32_t address, uint32_t pc, char* buffer, int blen) {
144 return snprintf(buffer, blen - 1, "$%08X", address + pc);
145}
146
147static int _decodeMemory(struct ARMMemoryAccess memory, int pc, char* buffer, int blen) {
148 if (blen <= 1) {
149 return 0;
150 }
151 int total = 0;
152 strncpy(buffer, "[", blen - 1);
153 ADVANCE(1);
154 int written;
155 if (memory.format & ARM_MEMORY_REGISTER_BASE) {
156 if (memory.baseReg == ARM_PC && memory.format & ARM_MEMORY_IMMEDIATE_OFFSET) {
157 written = _decodePCRelative(memory.format & ARM_MEMORY_OFFSET_SUBTRACT ? -memory.offset.immediate : memory.offset.immediate, pc & 0xFFFFFFFC, buffer, blen);
158 ADVANCE(written);
159 } else {
160 written = _decodeRegister(memory.baseReg, buffer, blen);
161 ADVANCE(written);
162 if (memory.format & (ARM_MEMORY_REGISTER_OFFSET | ARM_MEMORY_IMMEDIATE_OFFSET) && !(memory.format & ARM_MEMORY_POST_INCREMENT)) {
163 strncpy(buffer, ", ", blen - 1);
164 ADVANCE(2);
165 }
166 }
167 }
168 if (memory.format & ARM_MEMORY_POST_INCREMENT) {
169 strncpy(buffer, "], ", blen - 1);
170 ADVANCE(3);
171 }
172 if (memory.format & ARM_MEMORY_IMMEDIATE_OFFSET && memory.baseReg != ARM_PC) {
173 if (memory.format & ARM_MEMORY_OFFSET_SUBTRACT) {
174 written = snprintf(buffer, blen - 1, "#-%i", memory.offset.immediate);
175 ADVANCE(written);
176 } else {
177 written = snprintf(buffer, blen - 1, "#%i", memory.offset.immediate);
178 ADVANCE(written);
179 }
180 } else if (memory.format & ARM_MEMORY_REGISTER_OFFSET) {
181 if (memory.format & ARM_MEMORY_OFFSET_SUBTRACT) {
182 strncpy(buffer, "-", blen - 1);
183 ADVANCE(1);
184 }
185 written = _decodeRegister(memory.offset.reg, buffer, blen);
186 ADVANCE(written);
187 }
188 if (memory.format & ARM_MEMORY_SHIFTED_OFFSET) {
189 written = _decodeShift(memory.offset, false, buffer, blen);
190 ADVANCE(written);
191 }
192
193 if (!(memory.format & ARM_MEMORY_POST_INCREMENT)) {
194 strncpy(buffer, "]", blen - 1);
195 ADVANCE(1);
196 }
197 if ((memory.format & (ARM_MEMORY_PRE_INCREMENT | ARM_MEMORY_WRITEBACK)) == (ARM_MEMORY_PRE_INCREMENT | ARM_MEMORY_WRITEBACK)) {
198 strncpy(buffer, "!", blen - 1);
199 ADVANCE(1);
200 }
201 return total;
202}
203
204static int _decodeShift(union ARMOperand op, bool reg, char* buffer, int blen) {
205 if (blen <= 1) {
206 return 0;
207 }
208 int total = 0;
209 strncpy(buffer, ", ", blen - 1);
210 ADVANCE(2);
211 int written;
212 switch (op.shifterOp) {
213 case ARM_SHIFT_LSL:
214 strncpy(buffer, "lsl ", blen - 1);
215 ADVANCE(4);
216 break;
217 case ARM_SHIFT_LSR:
218 strncpy(buffer, "lsr ", blen - 1);
219 ADVANCE(4);
220 break;
221 case ARM_SHIFT_ASR:
222 strncpy(buffer, "asr ", blen - 1);
223 ADVANCE(4);
224 break;
225 case ARM_SHIFT_ROR:
226 strncpy(buffer, "ror ", blen - 1);
227 ADVANCE(4);
228 break;
229 case ARM_SHIFT_RRX:
230 strncpy(buffer, "rrx", blen - 1);
231 ADVANCE(3);
232 return total;
233 }
234 if (!reg) {
235 written = snprintf(buffer, blen - 1, "#%i", op.shifterImm);
236 } else {
237 written = _decodeRegister(op.shifterReg, buffer, blen);
238 }
239 ADVANCE(written);
240 return total;
241}
242
243static const char* _armMnemonicStrings[] = {
244 "ill",
245 "adc",
246 "add",
247 "and",
248 "asr",
249 "b",
250 "bic",
251 "bkpt",
252 "bl",
253 "blx",
254 "bx",
255 "cdp",
256 "clz",
257 "cmn",
258 "cmp",
259 "eor",
260 "ldc",
261 "ldm",
262 "ldr",
263 "lsl",
264 "lsr",
265 "mcr",
266 "mla",
267 "mov",
268 "mrc",
269 "mrs",
270 "msr",
271 "mul",
272 "mvn",
273 "neg",
274 "orr",
275 "ror",
276 "rsb",
277 "rsc",
278 "sbc",
279 "smlal",
280 "smull",
281 "stc",
282 "stm",
283 "str",
284 "sub",
285 "swi",
286 "swp",
287 "teq",
288 "tst",
289 "umlal",
290 "umull",
291
292 "ill"
293};
294
295static const char* _armDirectionStrings[] = {
296 "da",
297 "ia",
298 "db",
299 "ib"
300};
301
302static const char* _armAccessTypeStrings[] = {
303 "",
304 "b",
305 "h",
306 "",
307 "",
308 "",
309 "",
310 "",
311
312 "",
313 "sb",
314 "sh",
315 "",
316 "",
317 "",
318 "",
319 "",
320
321 "",
322 "bt",
323 "",
324 "",
325 "t",
326 "",
327 "",
328 ""
329};
330
331int ARMDisassemble(struct ARMInstructionInfo* info, uint32_t pc, char* buffer, int blen) {
332 const char* mnemonic = _armMnemonicStrings[info->mnemonic];
333 int written;
334 int total = 0;
335 const char* cond = "";
336 if (info->condition != ARM_CONDITION_AL && info->condition < ARM_CONDITION_NV) {
337 cond = _armConditions[info->condition];
338 }
339 const char* flags = "";
340 switch (info->mnemonic) {
341 case ARM_MN_LDM:
342 case ARM_MN_STM:
343 flags = _armDirectionStrings[MEMORY_FORMAT_TO_DIRECTION(info->memory.format)];
344 break;
345 case ARM_MN_LDR:
346 case ARM_MN_STR:
347 case ARM_MN_SWP:
348 flags = _armAccessTypeStrings[info->memory.width];
349 break;
350 case ARM_MN_ADD:
351 case ARM_MN_ADC:
352 case ARM_MN_AND:
353 case ARM_MN_BIC:
354 case ARM_MN_EOR:
355 case ARM_MN_MOV:
356 case ARM_MN_MVN:
357 case ARM_MN_ORR:
358 case ARM_MN_RSB:
359 case ARM_MN_RSC:
360 case ARM_MN_SBC:
361 case ARM_MN_SUB:
362 if (info->affectsCPSR && info->execMode == MODE_ARM) {
363 flags = "s";
364 }
365 break;
366 default:
367 break;
368 }
369 written = snprintf(buffer, blen - 1, "%s%s%s ", mnemonic, cond, flags);
370 ADVANCE(written);
371
372 switch (info->mnemonic) {
373 case ARM_MN_LDM:
374 case ARM_MN_STM:
375 written = _decodeRegister(info->memory.baseReg, buffer, blen);
376 ADVANCE(written);
377 if (info->memory.format & ARM_MEMORY_WRITEBACK) {
378 strncpy(buffer, "!", blen - 1);
379 ADVANCE(1);
380 }
381 strncpy(buffer, ", ", blen - 1);
382 ADVANCE(2);
383 written = _decodeRegisterList(info->op1.immediate, buffer, blen);
384 ADVANCE(written);
385 if (info->memory.format & ARM_MEMORY_SPSR_SWAP) {
386 strncpy(buffer, "^", blen - 1);
387 ADVANCE(1);
388 }
389 break;
390 case ARM_MN_B:
391 case ARM_MN_BL:
392 case ARM_MN_BLX:
393 if (info->operandFormat & ARM_OPERAND_IMMEDIATE_1) {
394 written = _decodePCRelative(info->op1.immediate, pc, buffer, blen);
395 ADVANCE(written);
396 }
397 break;
398 default:
399 if (info->operandFormat & ARM_OPERAND_COPROCESSOR) {
400 written = snprintf(buffer, blen - 1, "p%i, %i, ", info->cp.cp, info->cp.op1);
401 ADVANCE(written);
402 }
403 if (info->operandFormat & ARM_OPERAND_IMMEDIATE_1) {
404 written = snprintf(buffer, blen - 1, "#%i", info->op1.immediate);
405 ADVANCE(written);
406 } else if (info->operandFormat & ARM_OPERAND_MEMORY_1) {
407 written = _decodeMemory(info->memory, pc, buffer, blen);
408 ADVANCE(written);
409 } else if (info->operandFormat & ARM_OPERAND_REGISTER_1) {
410 written = _decodeRegister(info->op1.reg, buffer, blen);
411 ADVANCE(written);
412 if (info->op1.reg > ARM_PC) {
413 written = _decodePSR(info->op1.psrBits, buffer, blen);
414 ADVANCE(written);
415 }
416 } else if (info->operandFormat & ARM_OPERAND_COPROCESSOR_REG_1) {
417 written = snprintf(buffer, blen - 1, "c%i", info->op1.reg);
418 }
419 if (info->operandFormat & ARM_OPERAND_SHIFT_REGISTER_1) {
420 written = _decodeShift(info->op1, true, buffer, blen);
421 ADVANCE(written);
422 } else if (info->operandFormat & ARM_OPERAND_SHIFT_IMMEDIATE_1) {
423 written = _decodeShift(info->op1, false, buffer, blen);
424 ADVANCE(written);
425 }
426 if (info->operandFormat & ARM_OPERAND_2) {
427 strncpy(buffer, ", ", blen);
428 ADVANCE(2);
429 }
430 if (info->operandFormat & ARM_OPERAND_IMMEDIATE_2) {
431 written = snprintf(buffer, blen - 1, "#%i", info->op2.immediate);
432 ADVANCE(written);
433 } else if (info->operandFormat & ARM_OPERAND_MEMORY_2) {
434 written = _decodeMemory(info->memory, pc, buffer, blen);
435 ADVANCE(written);
436 } else if (info->operandFormat & ARM_OPERAND_REGISTER_2) {
437 written = _decodeRegister(info->op2.reg, buffer, blen);
438 ADVANCE(written);
439 } else if (info->operandFormat & ARM_OPERAND_COPROCESSOR_REG_2) {
440 written = snprintf(buffer, blen - 1, "c%i", info->op2.reg);
441 ADVANCE(written);
442 }
443 if (info->operandFormat & ARM_OPERAND_SHIFT_REGISTER_2) {
444 written = _decodeShift(info->op2, true, buffer, blen);
445 ADVANCE(written);
446 } else if (info->operandFormat & ARM_OPERAND_SHIFT_IMMEDIATE_2) {
447 written = _decodeShift(info->op2, false, buffer, blen);
448 ADVANCE(written);
449 }
450 if (info->operandFormat & ARM_OPERAND_3) {
451 strncpy(buffer, ", ", blen - 1);
452 ADVANCE(2);
453 }
454 if (info->operandFormat & ARM_OPERAND_IMMEDIATE_3) {
455 written = snprintf(buffer, blen - 1, "#%i", info->op3.immediate);
456 ADVANCE(written);
457 } else if (info->operandFormat & ARM_OPERAND_MEMORY_3) {
458 written = _decodeMemory(info->memory, pc, buffer, blen);
459 ADVANCE(written);
460 } else if (info->operandFormat & ARM_OPERAND_REGISTER_3) {
461 written = _decodeRegister(info->op3.reg, buffer, blen);
462 ADVANCE(written);
463 } else if (info->operandFormat & ARM_OPERAND_COPROCESSOR_REG_3) {
464 written = snprintf(buffer, blen - 1, "c%i", info->op3.reg);
465 ADVANCE(written);
466 }
467 if (info->operandFormat & ARM_OPERAND_SHIFT_REGISTER_3) {
468 written = _decodeShift(info->op3, true, buffer, blen);
469 ADVANCE(written);
470 } else if (info->operandFormat & ARM_OPERAND_SHIFT_IMMEDIATE_3) {
471 written = _decodeShift(info->op3, false, buffer, blen);
472 ADVANCE(written);
473 }
474 if (info->operandFormat & ARM_OPERAND_4) {
475 strncpy(buffer, ", ", blen - 1);
476 ADVANCE(2);
477 }
478 if (info->operandFormat & ARM_OPERAND_IMMEDIATE_4) {
479 written = snprintf(buffer, blen - 1, "#%i", info->op4.immediate);
480 ADVANCE(written);
481 } else if (info->operandFormat & ARM_OPERAND_MEMORY_4) {
482 written = _decodeMemory(info->memory, pc, buffer, blen);
483 ADVANCE(written);
484 } else if (info->operandFormat & ARM_OPERAND_REGISTER_4) {
485 written = _decodeRegister(info->op4.reg, buffer, blen);
486 ADVANCE(written);
487 } else if (info->operandFormat & ARM_OPERAND_COPROCESSOR_REG_4) {
488 written = snprintf(buffer, blen - 1, "c%i", info->op4.reg);
489 ADVANCE(written);
490 }
491 if (info->operandFormat & ARM_OPERAND_SHIFT_REGISTER_4) {
492 written = _decodeShift(info->op4, true, buffer, blen);
493 ADVANCE(written);
494 } else if (info->operandFormat & ARM_OPERAND_SHIFT_IMMEDIATE_4) {
495 written = _decodeShift(info->op4, false, buffer, blen);
496 ADVANCE(written);
497 }
498 if (info->cp.op2) {
499 written = snprintf(buffer, blen - 1, ", %i", info->cp.op2);
500 ADVANCE(written);
501 }
502 break;
503 }
504 buffer[blen - 1] = '\0';
505 return total;
506}