1 /*
2 * LZMA2 decoder
3 *
4 * Authors: Lasse Collin <lasse.collin@tukaani.org>
5 * Igor Pavlov <https://7-zip.org/>
6 *
7 * This file has been put into the public domain.
8 * You can do whatever you want with this file.
9 */
10
11 #include "xz_private.h"
12 #include "xz_lzma2.h"
13
14 /*
15 * Range decoder initialization eats the first five bytes of each LZMA chunk.
16 */
17 #define RC_INIT_BYTES 5
18
19 /*
20 * Minimum number of usable input buffer to safely decode one LZMA symbol.
21 * The worst case is that we decode 22 bits using probabilities and 26
22 * direct bits. This may decode at maximum of 20 bytes of input. However,
23 * lzma_main() does an extra normalization before returning, thus we
24 * need to put 21 here.
25 */
26 #define LZMA_IN_REQUIRED 21
27
28 /*
29 * Dictionary (history buffer)
30 *
31 * These are always true:
32 * start <= pos <= full <= end
33 * pos <= limit <= end
34 *
35 * In multi-call mode, also these are true:
36 * end == size
37 * size <= size_max
38 * allocated <= size
39 *
40 * Most of these variables are size_t to support single-call mode,
41 * in which the dictionary variables address the actual output
42 * buffer directly.
43 */
44 struct dictionary {
45 /* Beginning of the history buffer */
46 uint8_t *buf;
47
48 /* Old position in buf (before decoding more data) */
49 size_t start;
50
51 /* Position in buf */
52 size_t pos;
53
54 /*
55 * How full dictionary is. This is used to detect corrupt input that
56 * would read beyond the beginning of the uncompressed stream.
57 */
58 size_t full;
59
60 /* Write limit; we don't write to buf[limit] or later bytes. */
61 size_t limit;
62
63 /*
64 * End of the dictionary buffer. In multi-call mode, this is
65 * the same as the dictionary size. In single-call mode, this
66 * indicates the size of the output buffer.
67 */
68 size_t end;
69
70 /*
71 * Size of the dictionary as specified in Block Header. This is used
72 * together with "full" to detect corrupt input that would make us
73 * read beyond the beginning of the uncompressed stream.
74 */
75 uint32_t size;
76
77 /*
78 * Maximum allowed dictionary size in multi-call mode.
79 * This is ignored in single-call mode.
80 */
81 uint32_t size_max;
82
83 /*
84 * Amount of memory currently allocated for the dictionary.
85 * This is used only with XZ_DYNALLOC. (With XZ_PREALLOC,
86 * size_max is always the same as the allocated size.)
87 */
88 uint32_t allocated;
89
90 /* Operation mode */
91 enum xz_mode mode;
92 };
93
94 /* Range decoder */
95 struct rc_dec {
96 uint32_t range;
97 uint32_t code;
98
99 /*
100 * Number of initializing bytes remaining to be read
101 * by rc_read_init().
102 */
103 uint32_t init_bytes_left;
104
105 /*
106 * Buffer from which we read our input. It can be either
107 * temp.buf or the caller-provided input buffer.
108 */
109 const uint8_t *in;
110 size_t in_pos;
111 size_t in_limit;
112 };
113
114 /* Probabilities for a length decoder. */
115 struct lzma_len_dec {
116 /* Probability of match length being at least 10 */
117 uint16_t choice;
118
119 /* Probability of match length being at least 18 */
120 uint16_t choice2;
121
122 /* Probabilities for match lengths 2-9 */
123 uint16_t low[POS_STATES_MAX][LEN_LOW_SYMBOLS];
124
125 /* Probabilities for match lengths 10-17 */
126 uint16_t mid[POS_STATES_MAX][LEN_MID_SYMBOLS];
127
128 /* Probabilities for match lengths 18-273 */
129 uint16_t high[LEN_HIGH_SYMBOLS];
130 };
131
132 struct lzma_dec {
133 /* Distances of latest four matches */
134 uint32_t rep0;
135 uint32_t rep1;
136 uint32_t rep2;
137 uint32_t rep3;
138
139 /* Types of the most recently seen LZMA symbols */
140 enum lzma_state state;
141
142 /*
143 * Length of a match. This is updated so that dict_repeat can
144 * be called again to finish repeating the whole match.
145 */
146 uint32_t len;
147
148 /*
149 * LZMA properties or related bit masks (number of literal
150 * context bits, a mask derived from the number of literal
151 * position bits, and a mask derived from the number
152 * position bits)
153 */
154 uint32_t lc;
155 uint32_t literal_pos_mask; /* (1 << lp) - 1 */
156 uint32_t pos_mask; /* (1 << pb) - 1 */
157
158 /* If 1, it's a match. Otherwise it's a single 8-bit literal. */
159 uint16_t is_match[STATES][POS_STATES_MAX];
160
161 /* If 1, it's a repeated match. The distance is one of rep0 .. rep3. */
162 uint16_t is_rep[STATES];
163
164 /*
165 * If 0, distance of a repeated match is rep0.
166 * Otherwise check is_rep1.
167 */
168 uint16_t is_rep0[STATES];
169
170 /*
171 * If 0, distance of a repeated match is rep1.
172 * Otherwise check is_rep2.
173 */
174 uint16_t is_rep1[STATES];
175
176 /* If 0, distance of a repeated match is rep2. Otherwise it is rep3. */
177 uint16_t is_rep2[STATES];
178
179 /*
180 * If 1, the repeated match has length of one byte. Otherwise
181 * the length is decoded from rep_len_decoder.
182 */
183 uint16_t is_rep0_long[STATES][POS_STATES_MAX];
184
185 /*
186 * Probability tree for the highest two bits of the match
187 * distance. There is a separate probability tree for match
188 * lengths of 2 (i.e. MATCH_LEN_MIN), 3, 4, and [5, 273].
189 */
190 uint16_t dist_slot[DIST_STATES][DIST_SLOTS];
191
192 /*
193 * Probility trees for additional bits for match distance
194 * when the distance is in the range [4, 127].
195 */
196 uint16_t dist_special[FULL_DISTANCES - DIST_MODEL_END];
197
198 /*
199 * Probability tree for the lowest four bits of a match
200 * distance that is equal to or greater than 128.
201 */
202 uint16_t dist_align[ALIGN_SIZE];
203
204 /* Length of a normal match */
205 struct lzma_len_dec match_len_dec;
206
207 /* Length of a repeated match */
208 struct lzma_len_dec rep_len_dec;
209
210 /* Probabilities of literals */
211 uint16_t literal[LITERAL_CODERS_MAX][LITERAL_CODER_SIZE];
212 };
213
214 struct lzma2_dec {
215 /* Position in xz_dec_lzma2_run(). */
216 enum lzma2_seq {
217 SEQ_CONTROL,
218 SEQ_UNCOMPRESSED_1,
219 SEQ_UNCOMPRESSED_2,
220 SEQ_COMPRESSED_0,
221 SEQ_COMPRESSED_1,
222 SEQ_PROPERTIES,
223 SEQ_LZMA_PREPARE,
224 SEQ_LZMA_RUN,
225 SEQ_COPY
226 } sequence;
227
228 /* Next position after decoding the compressed size of the chunk. */
229 enum lzma2_seq next_sequence;
230
231 /* Uncompressed size of LZMA chunk (2 MiB at maximum) */
232 uint32_t uncompressed;
233
234 /*
235 * Compressed size of LZMA chunk or compressed/uncompressed
236 * size of uncompressed chunk (64 KiB at maximum)
237 */
238 uint32_t compressed;
239
240 /*
241 * True if dictionary reset is needed. This is false before
242 * the first chunk (LZMA or uncompressed).
243 */
244 bool need_dict_reset;
245
246 /*
247 * True if new LZMA properties are needed. This is false
248 * before the first LZMA chunk.
249 */
250 bool need_props;
251
252 #ifdef XZ_DEC_MICROLZMA
253 bool pedantic_microlzma;
254 #endif
255 };
256
257 struct xz_dec_lzma2 {
258 /*
259 * The order below is important on x86 to reduce code size and
260 * it shouldn't hurt on other platforms. Everything up to and
261 * including lzma.pos_mask are in the first 128 bytes on x86-32,
262 * which allows using smaller instructions to access those
263 * variables. On x86-64, fewer variables fit into the first 128
264 * bytes, but this is still the best order without sacrificing
265 * the readability by splitting the structures.
266 */
267 struct rc_dec rc;
268 struct dictionary dict;
269 struct lzma2_dec lzma2;
270 struct lzma_dec lzma;
271
272 /*
273 * Temporary buffer which holds small number of input bytes between
274 * decoder calls. See lzma2_lzma() for details.
275 */
276 struct {
277 uint32_t size;
278 uint8_t buf[3 * LZMA_IN_REQUIRED];
279 } temp;
280 };
281
282 /**************
283 * Dictionary *
284 **************/
285
286 /*
287 * Reset the dictionary state. When in single-call mode, set up the beginning
288 * of the dictionary to point to the actual output buffer.
289 */
dict_reset(struct dictionary * dict,struct xz_buf * b)290 static void dict_reset(struct dictionary *dict, struct xz_buf *b)
291 {
292 if (DEC_IS_SINGLE(dict->mode)) {
293 dict->buf = b->out + b->out_pos;
294 dict->end = b->out_size - b->out_pos;
295 }
296
297 dict->start = 0;
298 dict->pos = 0;
299 dict->limit = 0;
300 dict->full = 0;
301 }
302
303 /* Set dictionary write limit */
dict_limit(struct dictionary * dict,size_t out_max)304 static void dict_limit(struct dictionary *dict, size_t out_max)
305 {
306 if (dict->end - dict->pos <= out_max)
307 dict->limit = dict->end;
308 else
309 dict->limit = dict->pos + out_max;
310 }
311
312 /* Return true if at least one byte can be written into the dictionary. */
dict_has_space(const struct dictionary * dict)313 static inline bool dict_has_space(const struct dictionary *dict)
314 {
315 return dict->pos < dict->limit;
316 }
317
318 /*
319 * Get a byte from the dictionary at the given distance. The distance is
320 * assumed to valid, or as a special case, zero when the dictionary is
321 * still empty. This special case is needed for single-call decoding to
322 * avoid writing a '\0' to the end of the destination buffer.
323 */
dict_get(const struct dictionary * dict,uint32_t dist)324 static inline uint32_t dict_get(const struct dictionary *dict, uint32_t dist)
325 {
326 size_t offset = dict->pos - dist - 1;
327
328 if (dist >= dict->pos)
329 offset += dict->end;
330
331 return dict->full > 0 ? dict->buf[offset] : 0;
332 }
333
334 /*
335 * Put one byte into the dictionary. It is assumed that there is space for it.
336 */
dict_put(struct dictionary * dict,uint8_t byte)337 static inline void dict_put(struct dictionary *dict, uint8_t byte)
338 {
339 dict->buf[dict->pos++] = byte;
340
341 if (dict->full < dict->pos)
342 dict->full = dict->pos;
343 }
344
345 /*
346 * Repeat given number of bytes from the given distance. If the distance is
347 * invalid, false is returned. On success, true is returned and *len is
348 * updated to indicate how many bytes were left to be repeated.
349 */
dict_repeat(struct dictionary * dict,uint32_t * len,uint32_t dist)350 static bool dict_repeat(struct dictionary *dict, uint32_t *len, uint32_t dist)
351 {
352 size_t back;
353 uint32_t left;
354
355 if (dist >= dict->full || dist >= dict->size)
356 return false;
357
358 left = min_t(size_t, dict->limit - dict->pos, *len);
359 *len -= left;
360
361 back = dict->pos - dist - 1;
362 if (dist >= dict->pos)
363 back += dict->end;
364
365 do {
366 dict->buf[dict->pos++] = dict->buf[back++];
367 if (back == dict->end)
368 back = 0;
369 } while (--left > 0);
370
371 if (dict->full < dict->pos)
372 dict->full = dict->pos;
373
374 return true;
375 }
376
377 /* Copy uncompressed data as is from input to dictionary and output buffers. */
dict_uncompressed(struct dictionary * dict,struct xz_buf * b,uint32_t * left)378 static void dict_uncompressed(struct dictionary *dict, struct xz_buf *b,
379 uint32_t *left)
380 {
381 size_t copy_size;
382
383 while (*left > 0 && b->in_pos < b->in_size
384 && b->out_pos < b->out_size) {
385 copy_size = min(b->in_size - b->in_pos,
386 b->out_size - b->out_pos);
387 if (copy_size > dict->end - dict->pos)
388 copy_size = dict->end - dict->pos;
389 if (copy_size > *left)
390 copy_size = *left;
391
392 *left -= copy_size;
393
394 /*
395 * If doing in-place decompression in single-call mode and the
396 * uncompressed size of the file is larger than the caller
397 * thought (i.e. it is invalid input!), the buffers below may
398 * overlap and cause undefined behavior with memcpy().
399 * With valid inputs memcpy() would be fine here.
400 */
401 memmove(dict->buf + dict->pos, b->in + b->in_pos, copy_size);
402 dict->pos += copy_size;
403
404 if (dict->full < dict->pos)
405 dict->full = dict->pos;
406
407 if (DEC_IS_MULTI(dict->mode)) {
408 if (dict->pos == dict->end)
409 dict->pos = 0;
410
411 /*
412 * Like above but for multi-call mode: use memmove()
413 * to avoid undefined behavior with invalid input.
414 */
415 memmove(b->out + b->out_pos, b->in + b->in_pos,
416 copy_size);
417 }
418
419 dict->start = dict->pos;
420
421 b->out_pos += copy_size;
422 b->in_pos += copy_size;
423 }
424 }
425
426 #ifdef XZ_DEC_MICROLZMA
427 # define DICT_FLUSH_SUPPORTS_SKIPPING true
428 #else
429 # define DICT_FLUSH_SUPPORTS_SKIPPING false
430 #endif
431
432 /*
433 * Flush pending data from dictionary to b->out. It is assumed that there is
434 * enough space in b->out. This is guaranteed because caller uses dict_limit()
435 * before decoding data into the dictionary.
436 */
dict_flush(struct dictionary * dict,struct xz_buf * b)437 static uint32_t dict_flush(struct dictionary *dict, struct xz_buf *b)
438 {
439 size_t copy_size = dict->pos - dict->start;
440
441 if (DEC_IS_MULTI(dict->mode)) {
442 if (dict->pos == dict->end)
443 dict->pos = 0;
444
445 /*
446 * These buffers cannot overlap even if doing in-place
447 * decompression because in multi-call mode dict->buf
448 * has been allocated by us in this file; it's not
449 * provided by the caller like in single-call mode.
450 *
451 * With MicroLZMA, b->out can be NULL to skip bytes that
452 * the caller doesn't need. This cannot be done with XZ
453 * because it would break BCJ filters.
454 */
455 if (!DICT_FLUSH_SUPPORTS_SKIPPING || b->out != NULL)
456 memcpy(b->out + b->out_pos, dict->buf + dict->start,
457 copy_size);
458 }
459
460 dict->start = dict->pos;
461 b->out_pos += copy_size;
462 return copy_size;
463 }
464
465 /*****************
466 * Range decoder *
467 *****************/
468
469 /* Reset the range decoder. */
rc_reset(struct rc_dec * rc)470 static void rc_reset(struct rc_dec *rc)
471 {
472 rc->range = (uint32_t)-1;
473 rc->code = 0;
474 rc->init_bytes_left = RC_INIT_BYTES;
475 }
476
477 /*
478 * Read the first five initial bytes into rc->code if they haven't been
479 * read already. (Yes, the first byte gets completely ignored.)
480 */
rc_read_init(struct rc_dec * rc,struct xz_buf * b)481 static bool rc_read_init(struct rc_dec *rc, struct xz_buf *b)
482 {
483 while (rc->init_bytes_left > 0) {
484 if (b->in_pos == b->in_size)
485 return false;
486
487 rc->code = (rc->code << 8) + b->in[b->in_pos++];
488 --rc->init_bytes_left;
489 }
490
491 return true;
492 }
493
494 /* Return true if there may not be enough input for the next decoding loop. */
rc_limit_exceeded(const struct rc_dec * rc)495 static inline bool rc_limit_exceeded(const struct rc_dec *rc)
496 {
497 return rc->in_pos > rc->in_limit;
498 }
499
500 /*
501 * Return true if it is possible (from point of view of range decoder) that
502 * we have reached the end of the LZMA chunk.
503 */
rc_is_finished(const struct rc_dec * rc)504 static inline bool rc_is_finished(const struct rc_dec *rc)
505 {
506 return rc->code == 0;
507 }
508
509 /* Read the next input byte if needed. */
rc_normalize(struct rc_dec * rc)510 static __always_inline void rc_normalize(struct rc_dec *rc)
511 {
512 if (rc->range < RC_TOP_VALUE) {
513 rc->range <<= RC_SHIFT_BITS;
514 rc->code = (rc->code << RC_SHIFT_BITS) + rc->in[rc->in_pos++];
515 }
516 }
517
518 /*
519 * Decode one bit. In some versions, this function has been split in three
520 * functions so that the compiler is supposed to be able to more easily avoid
521 * an extra branch. In this particular version of the LZMA decoder, this
522 * doesn't seem to be a good idea (tested with GCC 3.3.6, 3.4.6, and 4.3.3
523 * on x86). Using a non-split version results in nicer looking code too.
524 *
525 * NOTE: This must return an int. Do not make it return a bool or the speed
526 * of the code generated by GCC 3.x decreases 10-15 %. (GCC 4.3 doesn't care,
527 * and it generates 10-20 % faster code than GCC 3.x from this file anyway.)
528 */
rc_bit(struct rc_dec * rc,uint16_t * prob)529 static __always_inline int rc_bit(struct rc_dec *rc, uint16_t *prob)
530 {
531 uint32_t bound;
532 int bit;
533
534 rc_normalize(rc);
535 bound = (rc->range >> RC_BIT_MODEL_TOTAL_BITS) * *prob;
536 if (rc->code < bound) {
537 rc->range = bound;
538 *prob += (RC_BIT_MODEL_TOTAL - *prob) >> RC_MOVE_BITS;
539 bit = 0;
540 } else {
541 rc->range -= bound;
542 rc->code -= bound;
543 *prob -= *prob >> RC_MOVE_BITS;
544 bit = 1;
545 }
546
547 return bit;
548 }
549
550 /* Decode a bittree starting from the most significant bit. */
rc_bittree(struct rc_dec * rc,uint16_t * probs,uint32_t limit)551 static __always_inline uint32_t rc_bittree(struct rc_dec *rc,
552 uint16_t *probs, uint32_t limit)
553 {
554 uint32_t symbol = 1;
555
556 do {
557 if (rc_bit(rc, &probs[symbol]))
558 symbol = (symbol << 1) + 1;
559 else
560 symbol <<= 1;
561 } while (symbol < limit);
562
563 return symbol;
564 }
565
566 /* Decode a bittree starting from the least significant bit. */
rc_bittree_reverse(struct rc_dec * rc,uint16_t * probs,uint32_t * dest,uint32_t limit)567 static __always_inline void rc_bittree_reverse(struct rc_dec *rc,
568 uint16_t *probs,
569 uint32_t *dest, uint32_t limit)
570 {
571 uint32_t symbol = 1;
572 uint32_t i = 0;
573
574 do {
575 if (rc_bit(rc, &probs[symbol])) {
576 symbol = (symbol << 1) + 1;
577 *dest += 1 << i;
578 } else {
579 symbol <<= 1;
580 }
581 } while (++i < limit);
582 }
583
584 /* Decode direct bits (fixed fifty-fifty probability) */
rc_direct(struct rc_dec * rc,uint32_t * dest,uint32_t limit)585 static inline void rc_direct(struct rc_dec *rc, uint32_t *dest, uint32_t limit)
586 {
587 uint32_t mask;
588
589 do {
590 rc_normalize(rc);
591 rc->range >>= 1;
592 rc->code -= rc->range;
593 mask = (uint32_t)0 - (rc->code >> 31);
594 rc->code += rc->range & mask;
595 *dest = (*dest << 1) + (mask + 1);
596 } while (--limit > 0);
597 }
598
599 /********
600 * LZMA *
601 ********/
602
603 /* Get pointer to literal coder probability array. */
lzma_literal_probs(struct xz_dec_lzma2 * s)604 static uint16_t *lzma_literal_probs(struct xz_dec_lzma2 *s)
605 {
606 uint32_t prev_byte = dict_get(&s->dict, 0);
607 uint32_t low = prev_byte >> (8 - s->lzma.lc);
608 uint32_t high = (s->dict.pos & s->lzma.literal_pos_mask) << s->lzma.lc;
609 return s->lzma.literal[low + high];
610 }
611
612 /* Decode a literal (one 8-bit byte) */
lzma_literal(struct xz_dec_lzma2 * s)613 static void lzma_literal(struct xz_dec_lzma2 *s)
614 {
615 uint16_t *probs;
616 uint32_t symbol;
617 uint32_t match_byte;
618 uint32_t match_bit;
619 uint32_t offset;
620 uint32_t i;
621
622 probs = lzma_literal_probs(s);
623
624 if (lzma_state_is_literal(s->lzma.state)) {
625 symbol = rc_bittree(&s->rc, probs, 0x100);
626 } else {
627 symbol = 1;
628 match_byte = dict_get(&s->dict, s->lzma.rep0) << 1;
629 offset = 0x100;
630
631 do {
632 match_bit = match_byte & offset;
633 match_byte <<= 1;
634 i = offset + match_bit + symbol;
635
636 if (rc_bit(&s->rc, &probs[i])) {
637 symbol = (symbol << 1) + 1;
638 offset &= match_bit;
639 } else {
640 symbol <<= 1;
641 offset &= ~match_bit;
642 }
643 } while (symbol < 0x100);
644 }
645
646 dict_put(&s->dict, (uint8_t)symbol);
647 lzma_state_literal(&s->lzma.state);
648 }
649
650 /* Decode the length of the match into s->lzma.len. */
lzma_len(struct xz_dec_lzma2 * s,struct lzma_len_dec * l,uint32_t pos_state)651 static void lzma_len(struct xz_dec_lzma2 *s, struct lzma_len_dec *l,
652 uint32_t pos_state)
653 {
654 uint16_t *probs;
655 uint32_t limit;
656
657 if (!rc_bit(&s->rc, &l->choice)) {
658 probs = l->low[pos_state];
659 limit = LEN_LOW_SYMBOLS;
660 s->lzma.len = MATCH_LEN_MIN;
661 } else {
662 if (!rc_bit(&s->rc, &l->choice2)) {
663 probs = l->mid[pos_state];
664 limit = LEN_MID_SYMBOLS;
665 s->lzma.len = MATCH_LEN_MIN + LEN_LOW_SYMBOLS;
666 } else {
667 probs = l->high;
668 limit = LEN_HIGH_SYMBOLS;
669 s->lzma.len = MATCH_LEN_MIN + LEN_LOW_SYMBOLS
670 + LEN_MID_SYMBOLS;
671 }
672 }
673
674 s->lzma.len += rc_bittree(&s->rc, probs, limit) - limit;
675 }
676
677 /* Decode a match. The distance will be stored in s->lzma.rep0. */
lzma_match(struct xz_dec_lzma2 * s,uint32_t pos_state)678 static void lzma_match(struct xz_dec_lzma2 *s, uint32_t pos_state)
679 {
680 uint16_t *probs;
681 uint32_t dist_slot;
682 uint32_t limit;
683
684 lzma_state_match(&s->lzma.state);
685
686 s->lzma.rep3 = s->lzma.rep2;
687 s->lzma.rep2 = s->lzma.rep1;
688 s->lzma.rep1 = s->lzma.rep0;
689
690 lzma_len(s, &s->lzma.match_len_dec, pos_state);
691
692 probs = s->lzma.dist_slot[lzma_get_dist_state(s->lzma.len)];
693 dist_slot = rc_bittree(&s->rc, probs, DIST_SLOTS) - DIST_SLOTS;
694
695 if (dist_slot < DIST_MODEL_START) {
696 s->lzma.rep0 = dist_slot;
697 } else {
698 limit = (dist_slot >> 1) - 1;
699 s->lzma.rep0 = 2 + (dist_slot & 1);
700
701 if (dist_slot < DIST_MODEL_END) {
702 s->lzma.rep0 <<= limit;
703 probs = s->lzma.dist_special + s->lzma.rep0
704 - dist_slot - 1;
705 rc_bittree_reverse(&s->rc, probs,
706 &s->lzma.rep0, limit);
707 } else {
708 rc_direct(&s->rc, &s->lzma.rep0, limit - ALIGN_BITS);
709 s->lzma.rep0 <<= ALIGN_BITS;
710 rc_bittree_reverse(&s->rc, s->lzma.dist_align,
711 &s->lzma.rep0, ALIGN_BITS);
712 }
713 }
714 }
715
716 /*
717 * Decode a repeated match. The distance is one of the four most recently
718 * seen matches. The distance will be stored in s->lzma.rep0.
719 */
lzma_rep_match(struct xz_dec_lzma2 * s,uint32_t pos_state)720 static void lzma_rep_match(struct xz_dec_lzma2 *s, uint32_t pos_state)
721 {
722 uint32_t tmp;
723
724 if (!rc_bit(&s->rc, &s->lzma.is_rep0[s->lzma.state])) {
725 if (!rc_bit(&s->rc, &s->lzma.is_rep0_long[
726 s->lzma.state][pos_state])) {
727 lzma_state_short_rep(&s->lzma.state);
728 s->lzma.len = 1;
729 return;
730 }
731 } else {
732 if (!rc_bit(&s->rc, &s->lzma.is_rep1[s->lzma.state])) {
733 tmp = s->lzma.rep1;
734 } else {
735 if (!rc_bit(&s->rc, &s->lzma.is_rep2[s->lzma.state])) {
736 tmp = s->lzma.rep2;
737 } else {
738 tmp = s->lzma.rep3;
739 s->lzma.rep3 = s->lzma.rep2;
740 }
741
742 s->lzma.rep2 = s->lzma.rep1;
743 }
744
745 s->lzma.rep1 = s->lzma.rep0;
746 s->lzma.rep0 = tmp;
747 }
748
749 lzma_state_long_rep(&s->lzma.state);
750 lzma_len(s, &s->lzma.rep_len_dec, pos_state);
751 }
752
753 /* LZMA decoder core */
lzma_main(struct xz_dec_lzma2 * s)754 static bool lzma_main(struct xz_dec_lzma2 *s)
755 {
756 uint32_t pos_state;
757
758 /*
759 * If the dictionary was reached during the previous call, try to
760 * finish the possibly pending repeat in the dictionary.
761 */
762 if (dict_has_space(&s->dict) && s->lzma.len > 0)
763 dict_repeat(&s->dict, &s->lzma.len, s->lzma.rep0);
764
765 /*
766 * Decode more LZMA symbols. One iteration may consume up to
767 * LZMA_IN_REQUIRED - 1 bytes.
768 */
769 while (dict_has_space(&s->dict) && !rc_limit_exceeded(&s->rc)) {
770 pos_state = s->dict.pos & s->lzma.pos_mask;
771
772 if (!rc_bit(&s->rc, &s->lzma.is_match[
773 s->lzma.state][pos_state])) {
774 lzma_literal(s);
775 } else {
776 if (rc_bit(&s->rc, &s->lzma.is_rep[s->lzma.state]))
777 lzma_rep_match(s, pos_state);
778 else
779 lzma_match(s, pos_state);
780
781 if (!dict_repeat(&s->dict, &s->lzma.len, s->lzma.rep0))
782 return false;
783 }
784 }
785
786 /*
787 * Having the range decoder always normalized when we are outside
788 * this function makes it easier to correctly handle end of the chunk.
789 */
790 rc_normalize(&s->rc);
791
792 return true;
793 }
794
795 /*
796 * Reset the LZMA decoder and range decoder state. Dictionary is not reset
797 * here, because LZMA state may be reset without resetting the dictionary.
798 */
lzma_reset(struct xz_dec_lzma2 * s)799 static void lzma_reset(struct xz_dec_lzma2 *s)
800 {
801 uint16_t *probs;
802 size_t i;
803
804 s->lzma.state = STATE_LIT_LIT;
805 s->lzma.rep0 = 0;
806 s->lzma.rep1 = 0;
807 s->lzma.rep2 = 0;
808 s->lzma.rep3 = 0;
809 s->lzma.len = 0;
810
811 /*
812 * All probabilities are initialized to the same value. This hack
813 * makes the code smaller by avoiding a separate loop for each
814 * probability array.
815 *
816 * This could be optimized so that only that part of literal
817 * probabilities that are actually required. In the common case
818 * we would write 12 KiB less.
819 */
820 probs = s->lzma.is_match[0];
821 for (i = 0; i < PROBS_TOTAL; ++i)
822 probs[i] = RC_BIT_MODEL_TOTAL / 2;
823
824 rc_reset(&s->rc);
825 }
826
827 /*
828 * Decode and validate LZMA properties (lc/lp/pb) and calculate the bit masks
829 * from the decoded lp and pb values. On success, the LZMA decoder state is
830 * reset and true is returned.
831 */
lzma_props(struct xz_dec_lzma2 * s,uint8_t props)832 static bool lzma_props(struct xz_dec_lzma2 *s, uint8_t props)
833 {
834 if (props > (4 * 5 + 4) * 9 + 8)
835 return false;
836
837 s->lzma.pos_mask = 0;
838 while (props >= 9 * 5) {
839 props -= 9 * 5;
840 ++s->lzma.pos_mask;
841 }
842
843 s->lzma.pos_mask = (1 << s->lzma.pos_mask) - 1;
844
845 s->lzma.literal_pos_mask = 0;
846 while (props >= 9) {
847 props -= 9;
848 ++s->lzma.literal_pos_mask;
849 }
850
851 s->lzma.lc = props;
852
853 if (s->lzma.lc + s->lzma.literal_pos_mask > 4)
854 return false;
855
856 s->lzma.literal_pos_mask = (1 << s->lzma.literal_pos_mask) - 1;
857
858 lzma_reset(s);
859
860 return true;
861 }
862
863 /*********
864 * LZMA2 *
865 *********/
866
867 /*
868 * The LZMA decoder assumes that if the input limit (s->rc.in_limit) hasn't
869 * been exceeded, it is safe to read up to LZMA_IN_REQUIRED bytes. This
870 * wrapper function takes care of making the LZMA decoder's assumption safe.
871 *
872 * As long as there is plenty of input left to be decoded in the current LZMA
873 * chunk, we decode directly from the caller-supplied input buffer until
874 * there's LZMA_IN_REQUIRED bytes left. Those remaining bytes are copied into
875 * s->temp.buf, which (hopefully) gets filled on the next call to this
876 * function. We decode a few bytes from the temporary buffer so that we can
877 * continue decoding from the caller-supplied input buffer again.
878 */
lzma2_lzma(struct xz_dec_lzma2 * s,struct xz_buf * b)879 static bool lzma2_lzma(struct xz_dec_lzma2 *s, struct xz_buf *b)
880 {
881 size_t in_avail;
882 uint32_t tmp;
883
884 in_avail = b->in_size - b->in_pos;
885 if (s->temp.size > 0 || s->lzma2.compressed == 0) {
886 tmp = 2 * LZMA_IN_REQUIRED - s->temp.size;
887 if (tmp > s->lzma2.compressed - s->temp.size)
888 tmp = s->lzma2.compressed - s->temp.size;
889 if (tmp > in_avail)
890 tmp = in_avail;
891
892 memcpy(s->temp.buf + s->temp.size, b->in + b->in_pos, tmp);
893
894 if (s->temp.size + tmp == s->lzma2.compressed) {
895 memzero(s->temp.buf + s->temp.size + tmp,
896 sizeof(s->temp.buf)
897 - s->temp.size - tmp);
898 s->rc.in_limit = s->temp.size + tmp;
899 } else if (s->temp.size + tmp < LZMA_IN_REQUIRED) {
900 s->temp.size += tmp;
901 b->in_pos += tmp;
902 return true;
903 } else {
904 s->rc.in_limit = s->temp.size + tmp - LZMA_IN_REQUIRED;
905 }
906
907 s->rc.in = s->temp.buf;
908 s->rc.in_pos = 0;
909
910 if (!lzma_main(s) || s->rc.in_pos > s->temp.size + tmp)
911 return false;
912
913 s->lzma2.compressed -= s->rc.in_pos;
914
915 if (s->rc.in_pos < s->temp.size) {
916 s->temp.size -= s->rc.in_pos;
917 memmove(s->temp.buf, s->temp.buf + s->rc.in_pos,
918 s->temp.size);
919 return true;
920 }
921
922 b->in_pos += s->rc.in_pos - s->temp.size;
923 s->temp.size = 0;
924 }
925
926 in_avail = b->in_size - b->in_pos;
927 if (in_avail >= LZMA_IN_REQUIRED) {
928 s->rc.in = b->in;
929 s->rc.in_pos = b->in_pos;
930
931 if (in_avail >= s->lzma2.compressed + LZMA_IN_REQUIRED)
932 s->rc.in_limit = b->in_pos + s->lzma2.compressed;
933 else
934 s->rc.in_limit = b->in_size - LZMA_IN_REQUIRED;
935
936 if (!lzma_main(s))
937 return false;
938
939 in_avail = s->rc.in_pos - b->in_pos;
940 if (in_avail > s->lzma2.compressed)
941 return false;
942
943 s->lzma2.compressed -= in_avail;
944 b->in_pos = s->rc.in_pos;
945 }
946
947 in_avail = b->in_size - b->in_pos;
948 if (in_avail < LZMA_IN_REQUIRED) {
949 if (in_avail > s->lzma2.compressed)
950 in_avail = s->lzma2.compressed;
951
952 memcpy(s->temp.buf, b->in + b->in_pos, in_avail);
953 s->temp.size = in_avail;
954 b->in_pos += in_avail;
955 }
956
957 return true;
958 }
959
960 /*
961 * Take care of the LZMA2 control layer, and forward the job of actual LZMA
962 * decoding or copying of uncompressed chunks to other functions.
963 */
xz_dec_lzma2_run(struct xz_dec_lzma2 * s,struct xz_buf * b)964 XZ_EXTERN enum xz_ret xz_dec_lzma2_run(struct xz_dec_lzma2 *s,
965 struct xz_buf *b)
966 {
967 uint32_t tmp;
968
969 while (b->in_pos < b->in_size || s->lzma2.sequence == SEQ_LZMA_RUN) {
970 switch (s->lzma2.sequence) {
971 case SEQ_CONTROL:
972 /*
973 * LZMA2 control byte
974 *
975 * Exact values:
976 * 0x00 End marker
977 * 0x01 Dictionary reset followed by
978 * an uncompressed chunk
979 * 0x02 Uncompressed chunk (no dictionary reset)
980 *
981 * Highest three bits (s->control & 0xE0):
982 * 0xE0 Dictionary reset, new properties and state
983 * reset, followed by LZMA compressed chunk
984 * 0xC0 New properties and state reset, followed
985 * by LZMA compressed chunk (no dictionary
986 * reset)
987 * 0xA0 State reset using old properties,
988 * followed by LZMA compressed chunk (no
989 * dictionary reset)
990 * 0x80 LZMA chunk (no dictionary or state reset)
991 *
992 * For LZMA compressed chunks, the lowest five bits
993 * (s->control & 1F) are the highest bits of the
994 * uncompressed size (bits 16-20).
995 *
996 * A new LZMA2 stream must begin with a dictionary
997 * reset. The first LZMA chunk must set new
998 * properties and reset the LZMA state.
999 *
1000 * Values that don't match anything described above
1001 * are invalid and we return XZ_DATA_ERROR.
1002 */
1003 tmp = b->in[b->in_pos++];
1004
1005 if (tmp == 0x00)
1006 return XZ_STREAM_END;
1007
1008 if (tmp >= 0xE0 || tmp == 0x01) {
1009 s->lzma2.need_props = true;
1010 s->lzma2.need_dict_reset = false;
1011 dict_reset(&s->dict, b);
1012 } else if (s->lzma2.need_dict_reset) {
1013 return XZ_DATA_ERROR;
1014 }
1015
1016 if (tmp >= 0x80) {
1017 s->lzma2.uncompressed = (tmp & 0x1F) << 16;
1018 s->lzma2.sequence = SEQ_UNCOMPRESSED_1;
1019
1020 if (tmp >= 0xC0) {
1021 /*
1022 * When there are new properties,
1023 * state reset is done at
1024 * SEQ_PROPERTIES.
1025 */
1026 s->lzma2.need_props = false;
1027 s->lzma2.next_sequence
1028 = SEQ_PROPERTIES;
1029
1030 } else if (s->lzma2.need_props) {
1031 return XZ_DATA_ERROR;
1032
1033 } else {
1034 s->lzma2.next_sequence
1035 = SEQ_LZMA_PREPARE;
1036 if (tmp >= 0xA0)
1037 lzma_reset(s);
1038 }
1039 } else {
1040 if (tmp > 0x02)
1041 return XZ_DATA_ERROR;
1042
1043 s->lzma2.sequence = SEQ_COMPRESSED_0;
1044 s->lzma2.next_sequence = SEQ_COPY;
1045 }
1046
1047 break;
1048
1049 case SEQ_UNCOMPRESSED_1:
1050 s->lzma2.uncompressed
1051 += (uint32_t)b->in[b->in_pos++] << 8;
1052 s->lzma2.sequence = SEQ_UNCOMPRESSED_2;
1053 break;
1054
1055 case SEQ_UNCOMPRESSED_2:
1056 s->lzma2.uncompressed
1057 += (uint32_t)b->in[b->in_pos++] + 1;
1058 s->lzma2.sequence = SEQ_COMPRESSED_0;
1059 break;
1060
1061 case SEQ_COMPRESSED_0:
1062 s->lzma2.compressed
1063 = (uint32_t)b->in[b->in_pos++] << 8;
1064 s->lzma2.sequence = SEQ_COMPRESSED_1;
1065 break;
1066
1067 case SEQ_COMPRESSED_1:
1068 s->lzma2.compressed
1069 += (uint32_t)b->in[b->in_pos++] + 1;
1070 s->lzma2.sequence = s->lzma2.next_sequence;
1071 break;
1072
1073 case SEQ_PROPERTIES:
1074 if (!lzma_props(s, b->in[b->in_pos++]))
1075 return XZ_DATA_ERROR;
1076
1077 s->lzma2.sequence = SEQ_LZMA_PREPARE;
1078
1079 fallthrough;
1080
1081 case SEQ_LZMA_PREPARE:
1082 if (s->lzma2.compressed < RC_INIT_BYTES)
1083 return XZ_DATA_ERROR;
1084
1085 if (!rc_read_init(&s->rc, b))
1086 return XZ_OK;
1087
1088 s->lzma2.compressed -= RC_INIT_BYTES;
1089 s->lzma2.sequence = SEQ_LZMA_RUN;
1090
1091 fallthrough;
1092
1093 case SEQ_LZMA_RUN:
1094 /*
1095 * Set dictionary limit to indicate how much we want
1096 * to be encoded at maximum. Decode new data into the
1097 * dictionary. Flush the new data from dictionary to
1098 * b->out. Check if we finished decoding this chunk.
1099 * In case the dictionary got full but we didn't fill
1100 * the output buffer yet, we may run this loop
1101 * multiple times without changing s->lzma2.sequence.
1102 */
1103 dict_limit(&s->dict, min_t(size_t,
1104 b->out_size - b->out_pos,
1105 s->lzma2.uncompressed));
1106 if (!lzma2_lzma(s, b))
1107 return XZ_DATA_ERROR;
1108
1109 s->lzma2.uncompressed -= dict_flush(&s->dict, b);
1110
1111 if (s->lzma2.uncompressed == 0) {
1112 if (s->lzma2.compressed > 0 || s->lzma.len > 0
1113 || !rc_is_finished(&s->rc))
1114 return XZ_DATA_ERROR;
1115
1116 rc_reset(&s->rc);
1117 s->lzma2.sequence = SEQ_CONTROL;
1118
1119 } else if (b->out_pos == b->out_size
1120 || (b->in_pos == b->in_size
1121 && s->temp.size
1122 < s->lzma2.compressed)) {
1123 return XZ_OK;
1124 }
1125
1126 break;
1127
1128 case SEQ_COPY:
1129 dict_uncompressed(&s->dict, b, &s->lzma2.compressed);
1130 if (s->lzma2.compressed > 0)
1131 return XZ_OK;
1132
1133 s->lzma2.sequence = SEQ_CONTROL;
1134 break;
1135 }
1136 }
1137
1138 return XZ_OK;
1139 }
1140
xz_dec_lzma2_create(enum xz_mode mode,uint32_t dict_max)1141 XZ_EXTERN struct xz_dec_lzma2 *xz_dec_lzma2_create(enum xz_mode mode,
1142 uint32_t dict_max)
1143 {
1144 struct xz_dec_lzma2 *s = kmalloc(sizeof(*s), GFP_KERNEL);
1145 if (s == NULL)
1146 return NULL;
1147
1148 s->dict.mode = mode;
1149 s->dict.size_max = dict_max;
1150
1151 if (DEC_IS_PREALLOC(mode)) {
1152 s->dict.buf = vmalloc(dict_max);
1153 if (s->dict.buf == NULL) {
1154 kfree(s);
1155 return NULL;
1156 }
1157 } else if (DEC_IS_DYNALLOC(mode)) {
1158 s->dict.buf = NULL;
1159 s->dict.allocated = 0;
1160 }
1161
1162 return s;
1163 }
1164
xz_dec_lzma2_reset(struct xz_dec_lzma2 * s,uint8_t props)1165 XZ_EXTERN enum xz_ret xz_dec_lzma2_reset(struct xz_dec_lzma2 *s, uint8_t props)
1166 {
1167 /* This limits dictionary size to 3 GiB to keep parsing simpler. */
1168 if (props > 39)
1169 return XZ_OPTIONS_ERROR;
1170
1171 s->dict.size = 2 + (props & 1);
1172 s->dict.size <<= (props >> 1) + 11;
1173
1174 if (DEC_IS_MULTI(s->dict.mode)) {
1175 if (s->dict.size > s->dict.size_max)
1176 return XZ_MEMLIMIT_ERROR;
1177
1178 s->dict.end = s->dict.size;
1179
1180 if (DEC_IS_DYNALLOC(s->dict.mode)) {
1181 if (s->dict.allocated < s->dict.size) {
1182 s->dict.allocated = s->dict.size;
1183 vfree(s->dict.buf);
1184 s->dict.buf = vmalloc(s->dict.size);
1185 if (s->dict.buf == NULL) {
1186 s->dict.allocated = 0;
1187 return XZ_MEM_ERROR;
1188 }
1189 }
1190 }
1191 }
1192
1193 s->lzma2.sequence = SEQ_CONTROL;
1194 s->lzma2.need_dict_reset = true;
1195
1196 s->temp.size = 0;
1197
1198 return XZ_OK;
1199 }
1200
xz_dec_lzma2_end(struct xz_dec_lzma2 * s)1201 XZ_EXTERN void xz_dec_lzma2_end(struct xz_dec_lzma2 *s)
1202 {
1203 if (DEC_IS_MULTI(s->dict.mode))
1204 vfree(s->dict.buf);
1205
1206 kfree(s);
1207 }
1208
1209 #ifdef XZ_DEC_MICROLZMA
1210 /* This is a wrapper struct to have a nice struct name in the public API. */
1211 struct xz_dec_microlzma {
1212 struct xz_dec_lzma2 s;
1213 };
1214
xz_dec_microlzma_run(struct xz_dec_microlzma * s_ptr,struct xz_buf * b)1215 enum xz_ret xz_dec_microlzma_run(struct xz_dec_microlzma *s_ptr,
1216 struct xz_buf *b)
1217 {
1218 struct xz_dec_lzma2 *s = &s_ptr->s;
1219
1220 /*
1221 * sequence is SEQ_PROPERTIES before the first input byte,
1222 * SEQ_LZMA_PREPARE until a total of five bytes have been read,
1223 * and SEQ_LZMA_RUN for the rest of the input stream.
1224 */
1225 if (s->lzma2.sequence != SEQ_LZMA_RUN) {
1226 if (s->lzma2.sequence == SEQ_PROPERTIES) {
1227 /* One byte is needed for the props. */
1228 if (b->in_pos >= b->in_size)
1229 return XZ_OK;
1230
1231 /*
1232 * Don't increment b->in_pos here. The same byte is
1233 * also passed to rc_read_init() which will ignore it.
1234 */
1235 if (!lzma_props(s, ~b->in[b->in_pos]))
1236 return XZ_DATA_ERROR;
1237
1238 s->lzma2.sequence = SEQ_LZMA_PREPARE;
1239 }
1240
1241 /*
1242 * xz_dec_microlzma_reset() doesn't validate the compressed
1243 * size so we do it here. We have to limit the maximum size
1244 * to avoid integer overflows in lzma2_lzma(). 3 GiB is a nice
1245 * round number and much more than users of this code should
1246 * ever need.
1247 */
1248 if (s->lzma2.compressed < RC_INIT_BYTES
1249 || s->lzma2.compressed > (3U << 30))
1250 return XZ_DATA_ERROR;
1251
1252 if (!rc_read_init(&s->rc, b))
1253 return XZ_OK;
1254
1255 s->lzma2.compressed -= RC_INIT_BYTES;
1256 s->lzma2.sequence = SEQ_LZMA_RUN;
1257
1258 dict_reset(&s->dict, b);
1259 }
1260
1261 /* This is to allow increasing b->out_size between calls. */
1262 if (DEC_IS_SINGLE(s->dict.mode))
1263 s->dict.end = b->out_size - b->out_pos;
1264
1265 while (true) {
1266 dict_limit(&s->dict, min_t(size_t, b->out_size - b->out_pos,
1267 s->lzma2.uncompressed));
1268
1269 if (!lzma2_lzma(s, b))
1270 return XZ_DATA_ERROR;
1271
1272 s->lzma2.uncompressed -= dict_flush(&s->dict, b);
1273
1274 if (s->lzma2.uncompressed == 0) {
1275 if (s->lzma2.pedantic_microlzma) {
1276 if (s->lzma2.compressed > 0 || s->lzma.len > 0
1277 || !rc_is_finished(&s->rc))
1278 return XZ_DATA_ERROR;
1279 }
1280
1281 return XZ_STREAM_END;
1282 }
1283
1284 if (b->out_pos == b->out_size)
1285 return XZ_OK;
1286
1287 if (b->in_pos == b->in_size
1288 && s->temp.size < s->lzma2.compressed)
1289 return XZ_OK;
1290 }
1291 }
1292
xz_dec_microlzma_alloc(enum xz_mode mode,uint32_t dict_size)1293 struct xz_dec_microlzma *xz_dec_microlzma_alloc(enum xz_mode mode,
1294 uint32_t dict_size)
1295 {
1296 struct xz_dec_microlzma *s;
1297
1298 /* Restrict dict_size to the same range as in the LZMA2 code. */
1299 if (dict_size < 4096 || dict_size > (3U << 30))
1300 return NULL;
1301
1302 s = kmalloc(sizeof(*s), GFP_KERNEL);
1303 if (s == NULL)
1304 return NULL;
1305
1306 s->s.dict.mode = mode;
1307 s->s.dict.size = dict_size;
1308
1309 if (DEC_IS_MULTI(mode)) {
1310 s->s.dict.end = dict_size;
1311
1312 s->s.dict.buf = vmalloc(dict_size);
1313 if (s->s.dict.buf == NULL) {
1314 kfree(s);
1315 return NULL;
1316 }
1317 }
1318
1319 return s;
1320 }
1321
xz_dec_microlzma_reset(struct xz_dec_microlzma * s,uint32_t comp_size,uint32_t uncomp_size,int uncomp_size_is_exact)1322 void xz_dec_microlzma_reset(struct xz_dec_microlzma *s, uint32_t comp_size,
1323 uint32_t uncomp_size, int uncomp_size_is_exact)
1324 {
1325 /*
1326 * comp_size is validated in xz_dec_microlzma_run().
1327 * uncomp_size can safely be anything.
1328 */
1329 s->s.lzma2.compressed = comp_size;
1330 s->s.lzma2.uncompressed = uncomp_size;
1331 s->s.lzma2.pedantic_microlzma = uncomp_size_is_exact;
1332
1333 s->s.lzma2.sequence = SEQ_PROPERTIES;
1334 s->s.temp.size = 0;
1335 }
1336
xz_dec_microlzma_end(struct xz_dec_microlzma * s)1337 void xz_dec_microlzma_end(struct xz_dec_microlzma *s)
1338 {
1339 if (DEC_IS_MULTI(s->s.dict.mode))
1340 vfree(s->s.dict.buf);
1341
1342 kfree(s);
1343 }
1344 #endif
1345