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1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * x86 instruction analysis
4 *
5 * Copyright (C) IBM Corporation, 2002, 2004, 2009
6 */
7
8#ifdef __KERNEL__
9#include <linux/string.h>
10#else
11#include <string.h>
12#endif
13#include "../include/asm/inat.h"
14#include "../include/asm/insn.h"
15
16/* Verify next sizeof(t) bytes can be on the same instruction */
17#define validate_next(t, insn, n) \
18 ((insn)->next_byte + sizeof(t) + n <= (insn)->end_kaddr)
19
20#define __get_next(t, insn) \
21 ({ t r = *(t*)insn->next_byte; insn->next_byte += sizeof(t); r; })
22
23#define __peek_nbyte_next(t, insn, n) \
24 ({ t r = *(t*)((insn)->next_byte + n); r; })
25
26#define get_next(t, insn) \
27 ({ if (unlikely(!validate_next(t, insn, 0))) goto err_out; __get_next(t, insn); })
28
29#define peek_nbyte_next(t, insn, n) \
30 ({ if (unlikely(!validate_next(t, insn, n))) goto err_out; __peek_nbyte_next(t, insn, n); })
31
32#define peek_next(t, insn) peek_nbyte_next(t, insn, 0)
33
34/**
35 * insn_init() - initialize struct insn
36 * @insn: &struct insn to be initialized
37 * @kaddr: address (in kernel memory) of instruction (or copy thereof)
38 * @x86_64: !0 for 64-bit kernel or 64-bit app
39 */
40void insn_init(struct insn *insn, const void *kaddr, int buf_len, int x86_64)
41{
42 /*
43 * Instructions longer than MAX_INSN_SIZE (15 bytes) are invalid
44 * even if the input buffer is long enough to hold them.
45 */
46 if (buf_len > MAX_INSN_SIZE)
47 buf_len = MAX_INSN_SIZE;
48
49 memset(insn, 0, sizeof(*insn));
50 insn->kaddr = kaddr;
51 insn->end_kaddr = kaddr + buf_len;
52 insn->next_byte = kaddr;
53 insn->x86_64 = x86_64 ? 1 : 0;
54 insn->opnd_bytes = 4;
55 if (x86_64)
56 insn->addr_bytes = 8;
57 else
58 insn->addr_bytes = 4;
59}
60
61/**
62 * insn_get_prefixes - scan x86 instruction prefix bytes
63 * @insn: &struct insn containing instruction
64 *
65 * Populates the @insn->prefixes bitmap, and updates @insn->next_byte
66 * to point to the (first) opcode. No effect if @insn->prefixes.got
67 * is already set.
68 */
69void insn_get_prefixes(struct insn *insn)
70{
71 struct insn_field *prefixes = &insn->prefixes;
72 insn_attr_t attr;
73 insn_byte_t b, lb;
74 int i, nb;
75
76 if (prefixes->got)
77 return;
78
79 nb = 0;
80 lb = 0;
81 b = peek_next(insn_byte_t, insn);
82 attr = inat_get_opcode_attribute(b);
83 while (inat_is_legacy_prefix(attr)) {
84 /* Skip if same prefix */
85 for (i = 0; i < nb; i++)
86 if (prefixes->bytes[i] == b)
87 goto found;
88 if (nb == 4)
89 /* Invalid instruction */
90 break;
91 prefixes->bytes[nb++] = b;
92 if (inat_is_address_size_prefix(attr)) {
93 /* address size switches 2/4 or 4/8 */
94 if (insn->x86_64)
95 insn->addr_bytes ^= 12;
96 else
97 insn->addr_bytes ^= 6;
98 } else if (inat_is_operand_size_prefix(attr)) {
99 /* oprand size switches 2/4 */
100 insn->opnd_bytes ^= 6;
101 }
102found:
103 prefixes->nbytes++;
104 insn->next_byte++;
105 lb = b;
106 b = peek_next(insn_byte_t, insn);
107 attr = inat_get_opcode_attribute(b);
108 }
109 /* Set the last prefix */
110 if (lb && lb != insn->prefixes.bytes[3]) {
111 if (unlikely(insn->prefixes.bytes[3])) {
112 /* Swap the last prefix */
113 b = insn->prefixes.bytes[3];
114 for (i = 0; i < nb; i++)
115 if (prefixes->bytes[i] == lb)
116 prefixes->bytes[i] = b;
117 }
118 insn->prefixes.bytes[3] = lb;
119 }
120
121 /* Decode REX prefix */
122 if (insn->x86_64) {
123 b = peek_next(insn_byte_t, insn);
124 attr = inat_get_opcode_attribute(b);
125 if (inat_is_rex_prefix(attr)) {
126 insn->rex_prefix.value = b;
127 insn->rex_prefix.nbytes = 1;
128 insn->next_byte++;
129 if (X86_REX_W(b))
130 /* REX.W overrides opnd_size */
131 insn->opnd_bytes = 8;
132 }
133 }
134 insn->rex_prefix.got = 1;
135
136 /* Decode VEX prefix */
137 b = peek_next(insn_byte_t, insn);
138 attr = inat_get_opcode_attribute(b);
139 if (inat_is_vex_prefix(attr)) {
140 insn_byte_t b2 = peek_nbyte_next(insn_byte_t, insn, 1);
141 if (!insn->x86_64) {
142 /*
143 * In 32-bits mode, if the [7:6] bits (mod bits of
144 * ModRM) on the second byte are not 11b, it is
145 * LDS or LES or BOUND.
146 */
147 if (X86_MODRM_MOD(b2) != 3)
148 goto vex_end;
149 }
150 insn->vex_prefix.bytes[0] = b;
151 insn->vex_prefix.bytes[1] = b2;
152 if (inat_is_evex_prefix(attr)) {
153 b2 = peek_nbyte_next(insn_byte_t, insn, 2);
154 insn->vex_prefix.bytes[2] = b2;
155 b2 = peek_nbyte_next(insn_byte_t, insn, 3);
156 insn->vex_prefix.bytes[3] = b2;
157 insn->vex_prefix.nbytes = 4;
158 insn->next_byte += 4;
159 if (insn->x86_64 && X86_VEX_W(b2))
160 /* VEX.W overrides opnd_size */
161 insn->opnd_bytes = 8;
162 } else if (inat_is_vex3_prefix(attr)) {
163 b2 = peek_nbyte_next(insn_byte_t, insn, 2);
164 insn->vex_prefix.bytes[2] = b2;
165 insn->vex_prefix.nbytes = 3;
166 insn->next_byte += 3;
167 if (insn->x86_64 && X86_VEX_W(b2))
168 /* VEX.W overrides opnd_size */
169 insn->opnd_bytes = 8;
170 } else {
171 /*
172 * For VEX2, fake VEX3-like byte#2.
173 * Makes it easier to decode vex.W, vex.vvvv,
174 * vex.L and vex.pp. Masking with 0x7f sets vex.W == 0.
175 */
176 insn->vex_prefix.bytes[2] = b2 & 0x7f;
177 insn->vex_prefix.nbytes = 2;
178 insn->next_byte += 2;
179 }
180 }
181vex_end:
182 insn->vex_prefix.got = 1;
183
184 prefixes->got = 1;
185
186err_out:
187 return;
188}
189
190/**
191 * insn_get_opcode - collect opcode(s)
192 * @insn: &struct insn containing instruction
193 *
194 * Populates @insn->opcode, updates @insn->next_byte to point past the
195 * opcode byte(s), and set @insn->attr (except for groups).
196 * If necessary, first collects any preceding (prefix) bytes.
197 * Sets @insn->opcode.value = opcode1. No effect if @insn->opcode.got
198 * is already 1.
199 */
200void insn_get_opcode(struct insn *insn)
201{
202 struct insn_field *opcode = &insn->opcode;
203 insn_byte_t op;
204 int pfx_id;
205 if (opcode->got)
206 return;
207 if (!insn->prefixes.got)
208 insn_get_prefixes(insn);
209
210 /* Get first opcode */
211 op = get_next(insn_byte_t, insn);
212 opcode->bytes[0] = op;
213 opcode->nbytes = 1;
214
215 /* Check if there is VEX prefix or not */
216 if (insn_is_avx(insn)) {
217 insn_byte_t m, p;
218 m = insn_vex_m_bits(insn);
219 p = insn_vex_p_bits(insn);
220 insn->attr = inat_get_avx_attribute(op, m, p);
221 if ((inat_must_evex(insn->attr) && !insn_is_evex(insn)) ||
222 (!inat_accept_vex(insn->attr) &&
223 !inat_is_group(insn->attr)))
224 insn->attr = 0; /* This instruction is bad */
225 goto end; /* VEX has only 1 byte for opcode */
226 }
227
228 insn->attr = inat_get_opcode_attribute(op);
229 while (inat_is_escape(insn->attr)) {
230 /* Get escaped opcode */
231 op = get_next(insn_byte_t, insn);
232 opcode->bytes[opcode->nbytes++] = op;
233 pfx_id = insn_last_prefix_id(insn);
234 insn->attr = inat_get_escape_attribute(op, pfx_id, insn->attr);
235 }
236 if (inat_must_vex(insn->attr))
237 insn->attr = 0; /* This instruction is bad */
238end:
239 opcode->got = 1;
240
241err_out:
242 return;
243}
244
245/**
246 * insn_get_modrm - collect ModRM byte, if any
247 * @insn: &struct insn containing instruction
248 *
249 * Populates @insn->modrm and updates @insn->next_byte to point past the
250 * ModRM byte, if any. If necessary, first collects the preceding bytes
251 * (prefixes and opcode(s)). No effect if @insn->modrm.got is already 1.
252 */
253void insn_get_modrm(struct insn *insn)
254{
255 struct insn_field *modrm = &insn->modrm;
256 insn_byte_t pfx_id, mod;
257 if (modrm->got)
258 return;
259 if (!insn->opcode.got)
260 insn_get_opcode(insn);
261
262 if (inat_has_modrm(insn->attr)) {
263 mod = get_next(insn_byte_t, insn);
264 modrm->value = mod;
265 modrm->nbytes = 1;
266 if (inat_is_group(insn->attr)) {
267 pfx_id = insn_last_prefix_id(insn);
268 insn->attr = inat_get_group_attribute(mod, pfx_id,
269 insn->attr);
270 if (insn_is_avx(insn) && !inat_accept_vex(insn->attr))
271 insn->attr = 0; /* This is bad */
272 }
273 }
274
275 if (insn->x86_64 && inat_is_force64(insn->attr))
276 insn->opnd_bytes = 8;
277 modrm->got = 1;
278
279err_out:
280 return;
281}
282
283
284/**
285 * insn_rip_relative() - Does instruction use RIP-relative addressing mode?
286 * @insn: &struct insn containing instruction
287 *
288 * If necessary, first collects the instruction up to and including the
289 * ModRM byte. No effect if @insn->x86_64 is 0.
290 */
291int insn_rip_relative(struct insn *insn)
292{
293 struct insn_field *modrm = &insn->modrm;
294
295 if (!insn->x86_64)
296 return 0;
297 if (!modrm->got)
298 insn_get_modrm(insn);
299 /*
300 * For rip-relative instructions, the mod field (top 2 bits)
301 * is zero and the r/m field (bottom 3 bits) is 0x5.
302 */
303 return (modrm->nbytes && (modrm->value & 0xc7) == 0x5);
304}
305
306/**
307 * insn_get_sib() - Get the SIB byte of instruction
308 * @insn: &struct insn containing instruction
309 *
310 * If necessary, first collects the instruction up to and including the
311 * ModRM byte.
312 */
313void insn_get_sib(struct insn *insn)
314{
315 insn_byte_t modrm;
316
317 if (insn->sib.got)
318 return;
319 if (!insn->modrm.got)
320 insn_get_modrm(insn);
321 if (insn->modrm.nbytes) {
322 modrm = (insn_byte_t)insn->modrm.value;
323 if (insn->addr_bytes != 2 &&
324 X86_MODRM_MOD(modrm) != 3 && X86_MODRM_RM(modrm) == 4) {
325 insn->sib.value = get_next(insn_byte_t, insn);
326 insn->sib.nbytes = 1;
327 }
328 }
329 insn->sib.got = 1;
330
331err_out:
332 return;
333}
334
335
336/**
337 * insn_get_displacement() - Get the displacement of instruction
338 * @insn: &struct insn containing instruction
339 *
340 * If necessary, first collects the instruction up to and including the
341 * SIB byte.
342 * Displacement value is sign-expanded.
343 */
344void insn_get_displacement(struct insn *insn)
345{
346 insn_byte_t mod, rm, base;
347
348 if (insn->displacement.got)
349 return;
350 if (!insn->sib.got)
351 insn_get_sib(insn);
352 if (insn->modrm.nbytes) {
353 /*
354 * Interpreting the modrm byte:
355 * mod = 00 - no displacement fields (exceptions below)
356 * mod = 01 - 1-byte displacement field
357 * mod = 10 - displacement field is 4 bytes, or 2 bytes if
358 * address size = 2 (0x67 prefix in 32-bit mode)
359 * mod = 11 - no memory operand
360 *
361 * If address size = 2...
362 * mod = 00, r/m = 110 - displacement field is 2 bytes
363 *
364 * If address size != 2...
365 * mod != 11, r/m = 100 - SIB byte exists
366 * mod = 00, SIB base = 101 - displacement field is 4 bytes
367 * mod = 00, r/m = 101 - rip-relative addressing, displacement
368 * field is 4 bytes
369 */
370 mod = X86_MODRM_MOD(insn->modrm.value);
371 rm = X86_MODRM_RM(insn->modrm.value);
372 base = X86_SIB_BASE(insn->sib.value);
373 if (mod == 3)
374 goto out;
375 if (mod == 1) {
376 insn->displacement.value = get_next(signed char, insn);
377 insn->displacement.nbytes = 1;
378 } else if (insn->addr_bytes == 2) {
379 if ((mod == 0 && rm == 6) || mod == 2) {
380 insn->displacement.value =
381 get_next(short, insn);
382 insn->displacement.nbytes = 2;
383 }
384 } else {
385 if ((mod == 0 && rm == 5) || mod == 2 ||
386 (mod == 0 && base == 5)) {
387 insn->displacement.value = get_next(int, insn);
388 insn->displacement.nbytes = 4;
389 }
390 }
391 }
392out:
393 insn->displacement.got = 1;
394
395err_out:
396 return;
397}
398
399/* Decode moffset16/32/64. Return 0 if failed */
400static int __get_moffset(struct insn *insn)
401{
402 switch (insn->addr_bytes) {
403 case 2:
404 insn->moffset1.value = get_next(short, insn);
405 insn->moffset1.nbytes = 2;
406 break;
407 case 4:
408 insn->moffset1.value = get_next(int, insn);
409 insn->moffset1.nbytes = 4;
410 break;
411 case 8:
412 insn->moffset1.value = get_next(int, insn);
413 insn->moffset1.nbytes = 4;
414 insn->moffset2.value = get_next(int, insn);
415 insn->moffset2.nbytes = 4;
416 break;
417 default: /* opnd_bytes must be modified manually */
418 goto err_out;
419 }
420 insn->moffset1.got = insn->moffset2.got = 1;
421
422 return 1;
423
424err_out:
425 return 0;
426}
427
428/* Decode imm v32(Iz). Return 0 if failed */
429static int __get_immv32(struct insn *insn)
430{
431 switch (insn->opnd_bytes) {
432 case 2:
433 insn->immediate.value = get_next(short, insn);
434 insn->immediate.nbytes = 2;
435 break;
436 case 4:
437 case 8:
438 insn->immediate.value = get_next(int, insn);
439 insn->immediate.nbytes = 4;
440 break;
441 default: /* opnd_bytes must be modified manually */
442 goto err_out;
443 }
444
445 return 1;
446
447err_out:
448 return 0;
449}
450
451/* Decode imm v64(Iv/Ov), Return 0 if failed */
452static int __get_immv(struct insn *insn)
453{
454 switch (insn->opnd_bytes) {
455 case 2:
456 insn->immediate1.value = get_next(short, insn);
457 insn->immediate1.nbytes = 2;
458 break;
459 case 4:
460 insn->immediate1.value = get_next(int, insn);
461 insn->immediate1.nbytes = 4;
462 break;
463 case 8:
464 insn->immediate1.value = get_next(int, insn);
465 insn->immediate1.nbytes = 4;
466 insn->immediate2.value = get_next(int, insn);
467 insn->immediate2.nbytes = 4;
468 break;
469 default: /* opnd_bytes must be modified manually */
470 goto err_out;
471 }
472 insn->immediate1.got = insn->immediate2.got = 1;
473
474 return 1;
475err_out:
476 return 0;
477}
478
479/* Decode ptr16:16/32(Ap) */
480static int __get_immptr(struct insn *insn)
481{
482 switch (insn->opnd_bytes) {
483 case 2:
484 insn->immediate1.value = get_next(short, insn);
485 insn->immediate1.nbytes = 2;
486 break;
487 case 4:
488 insn->immediate1.value = get_next(int, insn);
489 insn->immediate1.nbytes = 4;
490 break;
491 case 8:
492 /* ptr16:64 is not exist (no segment) */
493 return 0;
494 default: /* opnd_bytes must be modified manually */
495 goto err_out;
496 }
497 insn->immediate2.value = get_next(unsigned short, insn);
498 insn->immediate2.nbytes = 2;
499 insn->immediate1.got = insn->immediate2.got = 1;
500
501 return 1;
502err_out:
503 return 0;
504}
505
506/**
507 * insn_get_immediate() - Get the immediates of instruction
508 * @insn: &struct insn containing instruction
509 *
510 * If necessary, first collects the instruction up to and including the
511 * displacement bytes.
512 * Basically, most of immediates are sign-expanded. Unsigned-value can be
513 * get by bit masking with ((1 << (nbytes * 8)) - 1)
514 */
515void insn_get_immediate(struct insn *insn)
516{
517 if (insn->immediate.got)
518 return;
519 if (!insn->displacement.got)
520 insn_get_displacement(insn);
521
522 if (inat_has_moffset(insn->attr)) {
523 if (!__get_moffset(insn))
524 goto err_out;
525 goto done;
526 }
527
528 if (!inat_has_immediate(insn->attr))
529 /* no immediates */
530 goto done;
531
532 switch (inat_immediate_size(insn->attr)) {
533 case INAT_IMM_BYTE:
534 insn->immediate.value = get_next(signed char, insn);
535 insn->immediate.nbytes = 1;
536 break;
537 case INAT_IMM_WORD:
538 insn->immediate.value = get_next(short, insn);
539 insn->immediate.nbytes = 2;
540 break;
541 case INAT_IMM_DWORD:
542 insn->immediate.value = get_next(int, insn);
543 insn->immediate.nbytes = 4;
544 break;
545 case INAT_IMM_QWORD:
546 insn->immediate1.value = get_next(int, insn);
547 insn->immediate1.nbytes = 4;
548 insn->immediate2.value = get_next(int, insn);
549 insn->immediate2.nbytes = 4;
550 break;
551 case INAT_IMM_PTR:
552 if (!__get_immptr(insn))
553 goto err_out;
554 break;
555 case INAT_IMM_VWORD32:
556 if (!__get_immv32(insn))
557 goto err_out;
558 break;
559 case INAT_IMM_VWORD:
560 if (!__get_immv(insn))
561 goto err_out;
562 break;
563 default:
564 /* Here, insn must have an immediate, but failed */
565 goto err_out;
566 }
567 if (inat_has_second_immediate(insn->attr)) {
568 insn->immediate2.value = get_next(signed char, insn);
569 insn->immediate2.nbytes = 1;
570 }
571done:
572 insn->immediate.got = 1;
573
574err_out:
575 return;
576}
577
578/**
579 * insn_get_length() - Get the length of instruction
580 * @insn: &struct insn containing instruction
581 *
582 * If necessary, first collects the instruction up to and including the
583 * immediates bytes.
584 */
585void insn_get_length(struct insn *insn)
586{
587 if (insn->length)
588 return;
589 if (!insn->immediate.got)
590 insn_get_immediate(insn);
591 insn->length = (unsigned char)((unsigned long)insn->next_byte
592 - (unsigned long)insn->kaddr);
593}