1 /*
2 * x86 instruction analysis
3 *
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License as published by
6 * the Free Software Foundation; either version 2 of the License, or
7 * (at your option) any later version.
8 *
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * GNU General Public License for more details.
13 *
14 * You should have received a copy of the GNU General Public License
15 * along with this program; if not, write to the Free Software
16 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
17 *
18 * Copyright (C) IBM Corporation, 2002, 2004, 2009
19 */
20
21 #ifdef __KERNEL__
22 #include <linux/string.h>
23 #else
24 #include <string.h>
25 #endif
26 #include <asm/inat.h>
27 #include <asm/insn.h>
28
29 /* Verify next sizeof(t) bytes can be on the same instruction */
30 #define validate_next(t, insn, n) \
31 ((insn)->next_byte + sizeof(t) + n - (insn)->kaddr <= MAX_INSN_SIZE)
32
33 #define __get_next(t, insn) \
34 ({ t r = *(t*)insn->next_byte; insn->next_byte += sizeof(t); r; })
35
36 #define __peek_nbyte_next(t, insn, n) \
37 ({ t r = *(t*)((insn)->next_byte + n); r; })
38
39 #define get_next(t, insn) \
40 ({ if (unlikely(!validate_next(t, insn, 0))) goto err_out; __get_next(t, insn); })
41
42 #define peek_nbyte_next(t, insn, n) \
43 ({ if (unlikely(!validate_next(t, insn, n))) goto err_out; __peek_nbyte_next(t, insn, n); })
44
45 #define peek_next(t, insn) peek_nbyte_next(t, insn, 0)
46
47 /**
48 * insn_init() - initialize struct insn
49 * @insn: &struct insn to be initialized
50 * @kaddr: address (in kernel memory) of instruction (or copy thereof)
51 * @x86_64: !0 for 64-bit kernel or 64-bit app
52 */
insn_init(struct insn * insn,const void * kaddr,int x86_64)53 void insn_init(struct insn *insn, const void *kaddr, int x86_64)
54 {
55 memset(insn, 0, sizeof(*insn));
56 insn->kaddr = kaddr;
57 insn->next_byte = kaddr;
58 insn->x86_64 = x86_64 ? 1 : 0;
59 insn->opnd_bytes = 4;
60 if (x86_64)
61 insn->addr_bytes = 8;
62 else
63 insn->addr_bytes = 4;
64 }
65
66 /**
67 * insn_get_prefixes - scan x86 instruction prefix bytes
68 * @insn: &struct insn containing instruction
69 *
70 * Populates the @insn->prefixes bitmap, and updates @insn->next_byte
71 * to point to the (first) opcode. No effect if @insn->prefixes.got
72 * is already set.
73 */
insn_get_prefixes(struct insn * insn)74 void insn_get_prefixes(struct insn *insn)
75 {
76 struct insn_field *prefixes = &insn->prefixes;
77 insn_attr_t attr;
78 insn_byte_t b, lb;
79 int i, nb;
80
81 if (prefixes->got)
82 return;
83
84 nb = 0;
85 lb = 0;
86 b = peek_next(insn_byte_t, insn);
87 attr = inat_get_opcode_attribute(b);
88 while (inat_is_legacy_prefix(attr)) {
89 /* Skip if same prefix */
90 for (i = 0; i < nb; i++)
91 if (prefixes->bytes[i] == b)
92 goto found;
93 if (nb == 4)
94 /* Invalid instruction */
95 break;
96 prefixes->bytes[nb++] = b;
97 if (inat_is_address_size_prefix(attr)) {
98 /* address size switches 2/4 or 4/8 */
99 if (insn->x86_64)
100 insn->addr_bytes ^= 12;
101 else
102 insn->addr_bytes ^= 6;
103 } else if (inat_is_operand_size_prefix(attr)) {
104 /* oprand size switches 2/4 */
105 insn->opnd_bytes ^= 6;
106 }
107 found:
108 prefixes->nbytes++;
109 insn->next_byte++;
110 lb = b;
111 b = peek_next(insn_byte_t, insn);
112 attr = inat_get_opcode_attribute(b);
113 }
114 /* Set the last prefix */
115 if (lb && lb != insn->prefixes.bytes[3]) {
116 if (unlikely(insn->prefixes.bytes[3])) {
117 /* Swap the last prefix */
118 b = insn->prefixes.bytes[3];
119 for (i = 0; i < nb; i++)
120 if (prefixes->bytes[i] == lb)
121 prefixes->bytes[i] = b;
122 }
123 insn->prefixes.bytes[3] = lb;
124 }
125
126 /* Decode REX prefix */
127 if (insn->x86_64) {
128 b = peek_next(insn_byte_t, insn);
129 attr = inat_get_opcode_attribute(b);
130 if (inat_is_rex_prefix(attr)) {
131 insn->rex_prefix.value = b;
132 insn->rex_prefix.nbytes = 1;
133 insn->next_byte++;
134 if (X86_REX_W(b))
135 /* REX.W overrides opnd_size */
136 insn->opnd_bytes = 8;
137 }
138 }
139 insn->rex_prefix.got = 1;
140
141 /* Decode VEX prefix */
142 b = peek_next(insn_byte_t, insn);
143 attr = inat_get_opcode_attribute(b);
144 if (inat_is_vex_prefix(attr)) {
145 insn_byte_t b2 = peek_nbyte_next(insn_byte_t, insn, 1);
146 if (!insn->x86_64) {
147 /*
148 * In 32-bits mode, if the [7:6] bits (mod bits of
149 * ModRM) on the second byte are not 11b, it is
150 * LDS or LES.
151 */
152 if (X86_MODRM_MOD(b2) != 3)
153 goto vex_end;
154 }
155 insn->vex_prefix.bytes[0] = b;
156 insn->vex_prefix.bytes[1] = b2;
157 if (inat_is_vex3_prefix(attr)) {
158 b2 = peek_nbyte_next(insn_byte_t, insn, 2);
159 insn->vex_prefix.bytes[2] = b2;
160 insn->vex_prefix.nbytes = 3;
161 insn->next_byte += 3;
162 if (insn->x86_64 && X86_VEX_W(b2))
163 /* VEX.W overrides opnd_size */
164 insn->opnd_bytes = 8;
165 } else {
166 insn->vex_prefix.nbytes = 2;
167 insn->next_byte += 2;
168 }
169 }
170 vex_end:
171 insn->vex_prefix.got = 1;
172
173 prefixes->got = 1;
174
175 err_out:
176 return;
177 }
178
179 /**
180 * insn_get_opcode - collect opcode(s)
181 * @insn: &struct insn containing instruction
182 *
183 * Populates @insn->opcode, updates @insn->next_byte to point past the
184 * opcode byte(s), and set @insn->attr (except for groups).
185 * If necessary, first collects any preceding (prefix) bytes.
186 * Sets @insn->opcode.value = opcode1. No effect if @insn->opcode.got
187 * is already 1.
188 */
insn_get_opcode(struct insn * insn)189 void insn_get_opcode(struct insn *insn)
190 {
191 struct insn_field *opcode = &insn->opcode;
192 insn_byte_t op;
193 int pfx_id;
194 if (opcode->got)
195 return;
196 if (!insn->prefixes.got)
197 insn_get_prefixes(insn);
198
199 /* Get first opcode */
200 op = get_next(insn_byte_t, insn);
201 opcode->bytes[0] = op;
202 opcode->nbytes = 1;
203
204 /* Check if there is VEX prefix or not */
205 if (insn_is_avx(insn)) {
206 insn_byte_t m, p;
207 m = insn_vex_m_bits(insn);
208 p = insn_vex_p_bits(insn);
209 insn->attr = inat_get_avx_attribute(op, m, p);
210 if (!inat_accept_vex(insn->attr) && !inat_is_group(insn->attr))
211 insn->attr = 0; /* This instruction is bad */
212 goto end; /* VEX has only 1 byte for opcode */
213 }
214
215 insn->attr = inat_get_opcode_attribute(op);
216 while (inat_is_escape(insn->attr)) {
217 /* Get escaped opcode */
218 op = get_next(insn_byte_t, insn);
219 opcode->bytes[opcode->nbytes++] = op;
220 pfx_id = insn_last_prefix_id(insn);
221 insn->attr = inat_get_escape_attribute(op, pfx_id, insn->attr);
222 }
223 if (inat_must_vex(insn->attr))
224 insn->attr = 0; /* This instruction is bad */
225 end:
226 opcode->got = 1;
227
228 err_out:
229 return;
230 }
231
232 /**
233 * insn_get_modrm - collect ModRM byte, if any
234 * @insn: &struct insn containing instruction
235 *
236 * Populates @insn->modrm and updates @insn->next_byte to point past the
237 * ModRM byte, if any. If necessary, first collects the preceding bytes
238 * (prefixes and opcode(s)). No effect if @insn->modrm.got is already 1.
239 */
insn_get_modrm(struct insn * insn)240 void insn_get_modrm(struct insn *insn)
241 {
242 struct insn_field *modrm = &insn->modrm;
243 insn_byte_t pfx_id, mod;
244 if (modrm->got)
245 return;
246 if (!insn->opcode.got)
247 insn_get_opcode(insn);
248
249 if (inat_has_modrm(insn->attr)) {
250 mod = get_next(insn_byte_t, insn);
251 modrm->value = mod;
252 modrm->nbytes = 1;
253 if (inat_is_group(insn->attr)) {
254 pfx_id = insn_last_prefix_id(insn);
255 insn->attr = inat_get_group_attribute(mod, pfx_id,
256 insn->attr);
257 if (insn_is_avx(insn) && !inat_accept_vex(insn->attr))
258 insn->attr = 0; /* This is bad */
259 }
260 }
261
262 if (insn->x86_64 && inat_is_force64(insn->attr))
263 insn->opnd_bytes = 8;
264 modrm->got = 1;
265
266 err_out:
267 return;
268 }
269
270
271 /**
272 * insn_rip_relative() - Does instruction use RIP-relative addressing mode?
273 * @insn: &struct insn containing instruction
274 *
275 * If necessary, first collects the instruction up to and including the
276 * ModRM byte. No effect if @insn->x86_64 is 0.
277 */
insn_rip_relative(struct insn * insn)278 int insn_rip_relative(struct insn *insn)
279 {
280 struct insn_field *modrm = &insn->modrm;
281
282 if (!insn->x86_64)
283 return 0;
284 if (!modrm->got)
285 insn_get_modrm(insn);
286 /*
287 * For rip-relative instructions, the mod field (top 2 bits)
288 * is zero and the r/m field (bottom 3 bits) is 0x5.
289 */
290 return (modrm->nbytes && (modrm->value & 0xc7) == 0x5);
291 }
292
293 /**
294 * insn_get_sib() - Get the SIB byte of instruction
295 * @insn: &struct insn containing instruction
296 *
297 * If necessary, first collects the instruction up to and including the
298 * ModRM byte.
299 */
insn_get_sib(struct insn * insn)300 void insn_get_sib(struct insn *insn)
301 {
302 insn_byte_t modrm;
303
304 if (insn->sib.got)
305 return;
306 if (!insn->modrm.got)
307 insn_get_modrm(insn);
308 if (insn->modrm.nbytes) {
309 modrm = (insn_byte_t)insn->modrm.value;
310 if (insn->addr_bytes != 2 &&
311 X86_MODRM_MOD(modrm) != 3 && X86_MODRM_RM(modrm) == 4) {
312 insn->sib.value = get_next(insn_byte_t, insn);
313 insn->sib.nbytes = 1;
314 }
315 }
316 insn->sib.got = 1;
317
318 err_out:
319 return;
320 }
321
322
323 /**
324 * insn_get_displacement() - Get the displacement of instruction
325 * @insn: &struct insn containing instruction
326 *
327 * If necessary, first collects the instruction up to and including the
328 * SIB byte.
329 * Displacement value is sign-expanded.
330 */
insn_get_displacement(struct insn * insn)331 void insn_get_displacement(struct insn *insn)
332 {
333 insn_byte_t mod, rm, base;
334
335 if (insn->displacement.got)
336 return;
337 if (!insn->sib.got)
338 insn_get_sib(insn);
339 if (insn->modrm.nbytes) {
340 /*
341 * Interpreting the modrm byte:
342 * mod = 00 - no displacement fields (exceptions below)
343 * mod = 01 - 1-byte displacement field
344 * mod = 10 - displacement field is 4 bytes, or 2 bytes if
345 * address size = 2 (0x67 prefix in 32-bit mode)
346 * mod = 11 - no memory operand
347 *
348 * If address size = 2...
349 * mod = 00, r/m = 110 - displacement field is 2 bytes
350 *
351 * If address size != 2...
352 * mod != 11, r/m = 100 - SIB byte exists
353 * mod = 00, SIB base = 101 - displacement field is 4 bytes
354 * mod = 00, r/m = 101 - rip-relative addressing, displacement
355 * field is 4 bytes
356 */
357 mod = X86_MODRM_MOD(insn->modrm.value);
358 rm = X86_MODRM_RM(insn->modrm.value);
359 base = X86_SIB_BASE(insn->sib.value);
360 if (mod == 3)
361 goto out;
362 if (mod == 1) {
363 insn->displacement.value = get_next(char, insn);
364 insn->displacement.nbytes = 1;
365 } else if (insn->addr_bytes == 2) {
366 if ((mod == 0 && rm == 6) || mod == 2) {
367 insn->displacement.value =
368 get_next(short, insn);
369 insn->displacement.nbytes = 2;
370 }
371 } else {
372 if ((mod == 0 && rm == 5) || mod == 2 ||
373 (mod == 0 && base == 5)) {
374 insn->displacement.value = get_next(int, insn);
375 insn->displacement.nbytes = 4;
376 }
377 }
378 }
379 out:
380 insn->displacement.got = 1;
381
382 err_out:
383 return;
384 }
385
386 /* Decode moffset16/32/64. Return 0 if failed */
__get_moffset(struct insn * insn)387 static int __get_moffset(struct insn *insn)
388 {
389 switch (insn->addr_bytes) {
390 case 2:
391 insn->moffset1.value = get_next(short, insn);
392 insn->moffset1.nbytes = 2;
393 break;
394 case 4:
395 insn->moffset1.value = get_next(int, insn);
396 insn->moffset1.nbytes = 4;
397 break;
398 case 8:
399 insn->moffset1.value = get_next(int, insn);
400 insn->moffset1.nbytes = 4;
401 insn->moffset2.value = get_next(int, insn);
402 insn->moffset2.nbytes = 4;
403 break;
404 default: /* opnd_bytes must be modified manually */
405 goto err_out;
406 }
407 insn->moffset1.got = insn->moffset2.got = 1;
408
409 return 1;
410
411 err_out:
412 return 0;
413 }
414
415 /* Decode imm v32(Iz). Return 0 if failed */
__get_immv32(struct insn * insn)416 static int __get_immv32(struct insn *insn)
417 {
418 switch (insn->opnd_bytes) {
419 case 2:
420 insn->immediate.value = get_next(short, insn);
421 insn->immediate.nbytes = 2;
422 break;
423 case 4:
424 case 8:
425 insn->immediate.value = get_next(int, insn);
426 insn->immediate.nbytes = 4;
427 break;
428 default: /* opnd_bytes must be modified manually */
429 goto err_out;
430 }
431
432 return 1;
433
434 err_out:
435 return 0;
436 }
437
438 /* Decode imm v64(Iv/Ov), Return 0 if failed */
__get_immv(struct insn * insn)439 static int __get_immv(struct insn *insn)
440 {
441 switch (insn->opnd_bytes) {
442 case 2:
443 insn->immediate1.value = get_next(short, insn);
444 insn->immediate1.nbytes = 2;
445 break;
446 case 4:
447 insn->immediate1.value = get_next(int, insn);
448 insn->immediate1.nbytes = 4;
449 break;
450 case 8:
451 insn->immediate1.value = get_next(int, insn);
452 insn->immediate1.nbytes = 4;
453 insn->immediate2.value = get_next(int, insn);
454 insn->immediate2.nbytes = 4;
455 break;
456 default: /* opnd_bytes must be modified manually */
457 goto err_out;
458 }
459 insn->immediate1.got = insn->immediate2.got = 1;
460
461 return 1;
462 err_out:
463 return 0;
464 }
465
466 /* Decode ptr16:16/32(Ap) */
__get_immptr(struct insn * insn)467 static int __get_immptr(struct insn *insn)
468 {
469 switch (insn->opnd_bytes) {
470 case 2:
471 insn->immediate1.value = get_next(short, insn);
472 insn->immediate1.nbytes = 2;
473 break;
474 case 4:
475 insn->immediate1.value = get_next(int, insn);
476 insn->immediate1.nbytes = 4;
477 break;
478 case 8:
479 /* ptr16:64 is not exist (no segment) */
480 return 0;
481 default: /* opnd_bytes must be modified manually */
482 goto err_out;
483 }
484 insn->immediate2.value = get_next(unsigned short, insn);
485 insn->immediate2.nbytes = 2;
486 insn->immediate1.got = insn->immediate2.got = 1;
487
488 return 1;
489 err_out:
490 return 0;
491 }
492
493 /**
494 * insn_get_immediate() - Get the immediates of instruction
495 * @insn: &struct insn containing instruction
496 *
497 * If necessary, first collects the instruction up to and including the
498 * displacement bytes.
499 * Basically, most of immediates are sign-expanded. Unsigned-value can be
500 * get by bit masking with ((1 << (nbytes * 8)) - 1)
501 */
insn_get_immediate(struct insn * insn)502 void insn_get_immediate(struct insn *insn)
503 {
504 if (insn->immediate.got)
505 return;
506 if (!insn->displacement.got)
507 insn_get_displacement(insn);
508
509 if (inat_has_moffset(insn->attr)) {
510 if (!__get_moffset(insn))
511 goto err_out;
512 goto done;
513 }
514
515 if (!inat_has_immediate(insn->attr))
516 /* no immediates */
517 goto done;
518
519 switch (inat_immediate_size(insn->attr)) {
520 case INAT_IMM_BYTE:
521 insn->immediate.value = get_next(char, insn);
522 insn->immediate.nbytes = 1;
523 break;
524 case INAT_IMM_WORD:
525 insn->immediate.value = get_next(short, insn);
526 insn->immediate.nbytes = 2;
527 break;
528 case INAT_IMM_DWORD:
529 insn->immediate.value = get_next(int, insn);
530 insn->immediate.nbytes = 4;
531 break;
532 case INAT_IMM_QWORD:
533 insn->immediate1.value = get_next(int, insn);
534 insn->immediate1.nbytes = 4;
535 insn->immediate2.value = get_next(int, insn);
536 insn->immediate2.nbytes = 4;
537 break;
538 case INAT_IMM_PTR:
539 if (!__get_immptr(insn))
540 goto err_out;
541 break;
542 case INAT_IMM_VWORD32:
543 if (!__get_immv32(insn))
544 goto err_out;
545 break;
546 case INAT_IMM_VWORD:
547 if (!__get_immv(insn))
548 goto err_out;
549 break;
550 default:
551 /* Here, insn must have an immediate, but failed */
552 goto err_out;
553 }
554 if (inat_has_second_immediate(insn->attr)) {
555 insn->immediate2.value = get_next(char, insn);
556 insn->immediate2.nbytes = 1;
557 }
558 done:
559 insn->immediate.got = 1;
560
561 err_out:
562 return;
563 }
564
565 /**
566 * insn_get_length() - Get the length of instruction
567 * @insn: &struct insn containing instruction
568 *
569 * If necessary, first collects the instruction up to and including the
570 * immediates bytes.
571 */
insn_get_length(struct insn * insn)572 void insn_get_length(struct insn *insn)
573 {
574 if (insn->length)
575 return;
576 if (!insn->immediate.got)
577 insn_get_immediate(insn);
578 insn->length = (unsigned char)((unsigned long)insn->next_byte
579 - (unsigned long)insn->kaddr);
580 }
581