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)->end_kaddr)
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 buf_len,int x86_64)53 void insn_init(struct insn *insn, const void *kaddr, int buf_len, int x86_64)
54 {
55 /*
56 * Instructions longer than MAX_INSN_SIZE (15 bytes) are invalid
57 * even if the input buffer is long enough to hold them.
58 */
59 if (buf_len > MAX_INSN_SIZE)
60 buf_len = MAX_INSN_SIZE;
61
62 memset(insn, 0, sizeof(*insn));
63 insn->kaddr = kaddr;
64 insn->end_kaddr = kaddr + buf_len;
65 insn->next_byte = kaddr;
66 insn->x86_64 = x86_64 ? 1 : 0;
67 insn->opnd_bytes = 4;
68 if (x86_64)
69 insn->addr_bytes = 8;
70 else
71 insn->addr_bytes = 4;
72 }
73
74 /**
75 * insn_get_prefixes - scan x86 instruction prefix bytes
76 * @insn: &struct insn containing instruction
77 *
78 * Populates the @insn->prefixes bitmap, and updates @insn->next_byte
79 * to point to the (first) opcode. No effect if @insn->prefixes.got
80 * is already set.
81 */
insn_get_prefixes(struct insn * insn)82 void insn_get_prefixes(struct insn *insn)
83 {
84 struct insn_field *prefixes = &insn->prefixes;
85 insn_attr_t attr;
86 insn_byte_t b, lb;
87 int i, nb;
88
89 if (prefixes->got)
90 return;
91
92 nb = 0;
93 lb = 0;
94 b = peek_next(insn_byte_t, insn);
95 attr = inat_get_opcode_attribute(b);
96 while (inat_is_legacy_prefix(attr)) {
97 /* Skip if same prefix */
98 for (i = 0; i < nb; i++)
99 if (prefixes->bytes[i] == b)
100 goto found;
101 if (nb == 4)
102 /* Invalid instruction */
103 break;
104 prefixes->bytes[nb++] = b;
105 if (inat_is_address_size_prefix(attr)) {
106 /* address size switches 2/4 or 4/8 */
107 if (insn->x86_64)
108 insn->addr_bytes ^= 12;
109 else
110 insn->addr_bytes ^= 6;
111 } else if (inat_is_operand_size_prefix(attr)) {
112 /* oprand size switches 2/4 */
113 insn->opnd_bytes ^= 6;
114 }
115 found:
116 prefixes->nbytes++;
117 insn->next_byte++;
118 lb = b;
119 b = peek_next(insn_byte_t, insn);
120 attr = inat_get_opcode_attribute(b);
121 }
122 /* Set the last prefix */
123 if (lb && lb != insn->prefixes.bytes[3]) {
124 if (unlikely(insn->prefixes.bytes[3])) {
125 /* Swap the last prefix */
126 b = insn->prefixes.bytes[3];
127 for (i = 0; i < nb; i++)
128 if (prefixes->bytes[i] == lb)
129 prefixes->bytes[i] = b;
130 }
131 insn->prefixes.bytes[3] = lb;
132 }
133
134 /* Decode REX prefix */
135 if (insn->x86_64) {
136 b = peek_next(insn_byte_t, insn);
137 attr = inat_get_opcode_attribute(b);
138 if (inat_is_rex_prefix(attr)) {
139 insn->rex_prefix.value = b;
140 insn->rex_prefix.nbytes = 1;
141 insn->next_byte++;
142 if (X86_REX_W(b))
143 /* REX.W overrides opnd_size */
144 insn->opnd_bytes = 8;
145 }
146 }
147 insn->rex_prefix.got = 1;
148
149 /* Decode VEX prefix */
150 b = peek_next(insn_byte_t, insn);
151 attr = inat_get_opcode_attribute(b);
152 if (inat_is_vex_prefix(attr)) {
153 insn_byte_t b2 = peek_nbyte_next(insn_byte_t, insn, 1);
154 if (!insn->x86_64) {
155 /*
156 * In 32-bits mode, if the [7:6] bits (mod bits of
157 * ModRM) on the second byte are not 11b, it is
158 * LDS or LES.
159 */
160 if (X86_MODRM_MOD(b2) != 3)
161 goto vex_end;
162 }
163 insn->vex_prefix.bytes[0] = b;
164 insn->vex_prefix.bytes[1] = b2;
165 if (inat_is_vex3_prefix(attr)) {
166 b2 = peek_nbyte_next(insn_byte_t, insn, 2);
167 insn->vex_prefix.bytes[2] = b2;
168 insn->vex_prefix.nbytes = 3;
169 insn->next_byte += 3;
170 if (insn->x86_64 && X86_VEX_W(b2))
171 /* VEX.W overrides opnd_size */
172 insn->opnd_bytes = 8;
173 } else {
174 /*
175 * For VEX2, fake VEX3-like byte#2.
176 * Makes it easier to decode vex.W, vex.vvvv,
177 * vex.L and vex.pp. Masking with 0x7f sets vex.W == 0.
178 */
179 insn->vex_prefix.bytes[2] = b2 & 0x7f;
180 insn->vex_prefix.nbytes = 2;
181 insn->next_byte += 2;
182 }
183 }
184 vex_end:
185 insn->vex_prefix.got = 1;
186
187 prefixes->got = 1;
188
189 err_out:
190 return;
191 }
192
193 /**
194 * insn_get_opcode - collect opcode(s)
195 * @insn: &struct insn containing instruction
196 *
197 * Populates @insn->opcode, updates @insn->next_byte to point past the
198 * opcode byte(s), and set @insn->attr (except for groups).
199 * If necessary, first collects any preceding (prefix) bytes.
200 * Sets @insn->opcode.value = opcode1. No effect if @insn->opcode.got
201 * is already 1.
202 */
insn_get_opcode(struct insn * insn)203 void insn_get_opcode(struct insn *insn)
204 {
205 struct insn_field *opcode = &insn->opcode;
206 insn_byte_t op;
207 int pfx_id;
208 if (opcode->got)
209 return;
210 if (!insn->prefixes.got)
211 insn_get_prefixes(insn);
212
213 /* Get first opcode */
214 op = get_next(insn_byte_t, insn);
215 opcode->bytes[0] = op;
216 opcode->nbytes = 1;
217
218 /* Check if there is VEX prefix or not */
219 if (insn_is_avx(insn)) {
220 insn_byte_t m, p;
221 m = insn_vex_m_bits(insn);
222 p = insn_vex_p_bits(insn);
223 insn->attr = inat_get_avx_attribute(op, m, p);
224 if (!inat_accept_vex(insn->attr) && !inat_is_group(insn->attr))
225 insn->attr = 0; /* This instruction is bad */
226 goto end; /* VEX has only 1 byte for opcode */
227 }
228
229 insn->attr = inat_get_opcode_attribute(op);
230 while (inat_is_escape(insn->attr)) {
231 /* Get escaped opcode */
232 op = get_next(insn_byte_t, insn);
233 opcode->bytes[opcode->nbytes++] = op;
234 pfx_id = insn_last_prefix_id(insn);
235 insn->attr = inat_get_escape_attribute(op, pfx_id, insn->attr);
236 }
237 if (inat_must_vex(insn->attr))
238 insn->attr = 0; /* This instruction is bad */
239 end:
240 opcode->got = 1;
241
242 err_out:
243 return;
244 }
245
246 /**
247 * insn_get_modrm - collect ModRM byte, if any
248 * @insn: &struct insn containing instruction
249 *
250 * Populates @insn->modrm and updates @insn->next_byte to point past the
251 * ModRM byte, if any. If necessary, first collects the preceding bytes
252 * (prefixes and opcode(s)). No effect if @insn->modrm.got is already 1.
253 */
insn_get_modrm(struct insn * insn)254 void insn_get_modrm(struct insn *insn)
255 {
256 struct insn_field *modrm = &insn->modrm;
257 insn_byte_t pfx_id, mod;
258 if (modrm->got)
259 return;
260 if (!insn->opcode.got)
261 insn_get_opcode(insn);
262
263 if (inat_has_modrm(insn->attr)) {
264 mod = get_next(insn_byte_t, insn);
265 modrm->value = mod;
266 modrm->nbytes = 1;
267 if (inat_is_group(insn->attr)) {
268 pfx_id = insn_last_prefix_id(insn);
269 insn->attr = inat_get_group_attribute(mod, pfx_id,
270 insn->attr);
271 if (insn_is_avx(insn) && !inat_accept_vex(insn->attr))
272 insn->attr = 0; /* This is bad */
273 }
274 }
275
276 if (insn->x86_64 && inat_is_force64(insn->attr))
277 insn->opnd_bytes = 8;
278 modrm->got = 1;
279
280 err_out:
281 return;
282 }
283
284
285 /**
286 * insn_rip_relative() - Does instruction use RIP-relative addressing mode?
287 * @insn: &struct insn containing instruction
288 *
289 * If necessary, first collects the instruction up to and including the
290 * ModRM byte. No effect if @insn->x86_64 is 0.
291 */
insn_rip_relative(struct insn * insn)292 int insn_rip_relative(struct insn *insn)
293 {
294 struct insn_field *modrm = &insn->modrm;
295
296 if (!insn->x86_64)
297 return 0;
298 if (!modrm->got)
299 insn_get_modrm(insn);
300 /*
301 * For rip-relative instructions, the mod field (top 2 bits)
302 * is zero and the r/m field (bottom 3 bits) is 0x5.
303 */
304 return (modrm->nbytes && (modrm->value & 0xc7) == 0x5);
305 }
306
307 /**
308 * insn_get_sib() - Get the SIB byte of instruction
309 * @insn: &struct insn containing instruction
310 *
311 * If necessary, first collects the instruction up to and including the
312 * ModRM byte.
313 */
insn_get_sib(struct insn * insn)314 void insn_get_sib(struct insn *insn)
315 {
316 insn_byte_t modrm;
317
318 if (insn->sib.got)
319 return;
320 if (!insn->modrm.got)
321 insn_get_modrm(insn);
322 if (insn->modrm.nbytes) {
323 modrm = (insn_byte_t)insn->modrm.value;
324 if (insn->addr_bytes != 2 &&
325 X86_MODRM_MOD(modrm) != 3 && X86_MODRM_RM(modrm) == 4) {
326 insn->sib.value = get_next(insn_byte_t, insn);
327 insn->sib.nbytes = 1;
328 }
329 }
330 insn->sib.got = 1;
331
332 err_out:
333 return;
334 }
335
336
337 /**
338 * insn_get_displacement() - Get the displacement of instruction
339 * @insn: &struct insn containing instruction
340 *
341 * If necessary, first collects the instruction up to and including the
342 * SIB byte.
343 * Displacement value is sign-expanded.
344 */
insn_get_displacement(struct insn * insn)345 void insn_get_displacement(struct insn *insn)
346 {
347 insn_byte_t mod, rm, base;
348
349 if (insn->displacement.got)
350 return;
351 if (!insn->sib.got)
352 insn_get_sib(insn);
353 if (insn->modrm.nbytes) {
354 /*
355 * Interpreting the modrm byte:
356 * mod = 00 - no displacement fields (exceptions below)
357 * mod = 01 - 1-byte displacement field
358 * mod = 10 - displacement field is 4 bytes, or 2 bytes if
359 * address size = 2 (0x67 prefix in 32-bit mode)
360 * mod = 11 - no memory operand
361 *
362 * If address size = 2...
363 * mod = 00, r/m = 110 - displacement field is 2 bytes
364 *
365 * If address size != 2...
366 * mod != 11, r/m = 100 - SIB byte exists
367 * mod = 00, SIB base = 101 - displacement field is 4 bytes
368 * mod = 00, r/m = 101 - rip-relative addressing, displacement
369 * field is 4 bytes
370 */
371 mod = X86_MODRM_MOD(insn->modrm.value);
372 rm = X86_MODRM_RM(insn->modrm.value);
373 base = X86_SIB_BASE(insn->sib.value);
374 if (mod == 3)
375 goto out;
376 if (mod == 1) {
377 insn->displacement.value = get_next(char, insn);
378 insn->displacement.nbytes = 1;
379 } else if (insn->addr_bytes == 2) {
380 if ((mod == 0 && rm == 6) || mod == 2) {
381 insn->displacement.value =
382 get_next(short, insn);
383 insn->displacement.nbytes = 2;
384 }
385 } else {
386 if ((mod == 0 && rm == 5) || mod == 2 ||
387 (mod == 0 && base == 5)) {
388 insn->displacement.value = get_next(int, insn);
389 insn->displacement.nbytes = 4;
390 }
391 }
392 }
393 out:
394 insn->displacement.got = 1;
395
396 err_out:
397 return;
398 }
399
400 /* Decode moffset16/32/64. Return 0 if failed */
__get_moffset(struct insn * insn)401 static int __get_moffset(struct insn *insn)
402 {
403 switch (insn->addr_bytes) {
404 case 2:
405 insn->moffset1.value = get_next(short, insn);
406 insn->moffset1.nbytes = 2;
407 break;
408 case 4:
409 insn->moffset1.value = get_next(int, insn);
410 insn->moffset1.nbytes = 4;
411 break;
412 case 8:
413 insn->moffset1.value = get_next(int, insn);
414 insn->moffset1.nbytes = 4;
415 insn->moffset2.value = get_next(int, insn);
416 insn->moffset2.nbytes = 4;
417 break;
418 default: /* opnd_bytes must be modified manually */
419 goto err_out;
420 }
421 insn->moffset1.got = insn->moffset2.got = 1;
422
423 return 1;
424
425 err_out:
426 return 0;
427 }
428
429 /* Decode imm v32(Iz). Return 0 if failed */
__get_immv32(struct insn * insn)430 static int __get_immv32(struct insn *insn)
431 {
432 switch (insn->opnd_bytes) {
433 case 2:
434 insn->immediate.value = get_next(short, insn);
435 insn->immediate.nbytes = 2;
436 break;
437 case 4:
438 case 8:
439 insn->immediate.value = get_next(int, insn);
440 insn->immediate.nbytes = 4;
441 break;
442 default: /* opnd_bytes must be modified manually */
443 goto err_out;
444 }
445
446 return 1;
447
448 err_out:
449 return 0;
450 }
451
452 /* Decode imm v64(Iv/Ov), Return 0 if failed */
__get_immv(struct insn * insn)453 static int __get_immv(struct insn *insn)
454 {
455 switch (insn->opnd_bytes) {
456 case 2:
457 insn->immediate1.value = get_next(short, insn);
458 insn->immediate1.nbytes = 2;
459 break;
460 case 4:
461 insn->immediate1.value = get_next(int, insn);
462 insn->immediate1.nbytes = 4;
463 break;
464 case 8:
465 insn->immediate1.value = get_next(int, insn);
466 insn->immediate1.nbytes = 4;
467 insn->immediate2.value = get_next(int, insn);
468 insn->immediate2.nbytes = 4;
469 break;
470 default: /* opnd_bytes must be modified manually */
471 goto err_out;
472 }
473 insn->immediate1.got = insn->immediate2.got = 1;
474
475 return 1;
476 err_out:
477 return 0;
478 }
479
480 /* Decode ptr16:16/32(Ap) */
__get_immptr(struct insn * insn)481 static int __get_immptr(struct insn *insn)
482 {
483 switch (insn->opnd_bytes) {
484 case 2:
485 insn->immediate1.value = get_next(short, insn);
486 insn->immediate1.nbytes = 2;
487 break;
488 case 4:
489 insn->immediate1.value = get_next(int, insn);
490 insn->immediate1.nbytes = 4;
491 break;
492 case 8:
493 /* ptr16:64 is not exist (no segment) */
494 return 0;
495 default: /* opnd_bytes must be modified manually */
496 goto err_out;
497 }
498 insn->immediate2.value = get_next(unsigned short, insn);
499 insn->immediate2.nbytes = 2;
500 insn->immediate1.got = insn->immediate2.got = 1;
501
502 return 1;
503 err_out:
504 return 0;
505 }
506
507 /**
508 * insn_get_immediate() - Get the immediates of instruction
509 * @insn: &struct insn containing instruction
510 *
511 * If necessary, first collects the instruction up to and including the
512 * displacement bytes.
513 * Basically, most of immediates are sign-expanded. Unsigned-value can be
514 * get by bit masking with ((1 << (nbytes * 8)) - 1)
515 */
insn_get_immediate(struct insn * insn)516 void insn_get_immediate(struct insn *insn)
517 {
518 if (insn->immediate.got)
519 return;
520 if (!insn->displacement.got)
521 insn_get_displacement(insn);
522
523 if (inat_has_moffset(insn->attr)) {
524 if (!__get_moffset(insn))
525 goto err_out;
526 goto done;
527 }
528
529 if (!inat_has_immediate(insn->attr))
530 /* no immediates */
531 goto done;
532
533 switch (inat_immediate_size(insn->attr)) {
534 case INAT_IMM_BYTE:
535 insn->immediate.value = get_next(char, insn);
536 insn->immediate.nbytes = 1;
537 break;
538 case INAT_IMM_WORD:
539 insn->immediate.value = get_next(short, insn);
540 insn->immediate.nbytes = 2;
541 break;
542 case INAT_IMM_DWORD:
543 insn->immediate.value = get_next(int, insn);
544 insn->immediate.nbytes = 4;
545 break;
546 case INAT_IMM_QWORD:
547 insn->immediate1.value = get_next(int, insn);
548 insn->immediate1.nbytes = 4;
549 insn->immediate2.value = get_next(int, insn);
550 insn->immediate2.nbytes = 4;
551 break;
552 case INAT_IMM_PTR:
553 if (!__get_immptr(insn))
554 goto err_out;
555 break;
556 case INAT_IMM_VWORD32:
557 if (!__get_immv32(insn))
558 goto err_out;
559 break;
560 case INAT_IMM_VWORD:
561 if (!__get_immv(insn))
562 goto err_out;
563 break;
564 default:
565 /* Here, insn must have an immediate, but failed */
566 goto err_out;
567 }
568 if (inat_has_second_immediate(insn->attr)) {
569 insn->immediate2.value = get_next(char, insn);
570 insn->immediate2.nbytes = 1;
571 }
572 done:
573 insn->immediate.got = 1;
574
575 err_out:
576 return;
577 }
578
579 /**
580 * insn_get_length() - Get the length of instruction
581 * @insn: &struct insn containing instruction
582 *
583 * If necessary, first collects the instruction up to and including the
584 * immediates bytes.
585 */
insn_get_length(struct insn * insn)586 void insn_get_length(struct insn *insn)
587 {
588 if (insn->length)
589 return;
590 if (!insn->immediate.got)
591 insn_get_immediate(insn);
592 insn->length = (unsigned char)((unsigned long)insn->next_byte
593 - (unsigned long)insn->kaddr);
594 }
595