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
253 struct xz_dec_lzma2 {
254 /*
255 * The order below is important on x86 to reduce code size and
256 * it shouldn't hurt on other platforms. Everything up to and
257 * including lzma.pos_mask are in the first 128 bytes on x86-32,
258 * which allows using smaller instructions to access those
259 * variables. On x86-64, fewer variables fit into the first 128
260 * bytes, but this is still the best order without sacrificing
261 * the readability by splitting the structures.
262 */
263 struct rc_dec rc;
264 struct dictionary dict;
265 struct lzma2_dec lzma2;
266 struct lzma_dec lzma;
267
268 /*
269 * Temporary buffer which holds small number of input bytes between
270 * decoder calls. See lzma2_lzma() for details.
271 */
272 struct {
273 uint32_t size;
274 uint8_t buf[3 * LZMA_IN_REQUIRED];
275 } temp;
276 };
277
278 /**************
279 * Dictionary *
280 **************/
281
282 /*
283 * Reset the dictionary state. When in single-call mode, set up the beginning
284 * of the dictionary to point to the actual output buffer.
285 */
dict_reset(struct dictionary * dict,struct xz_buf * b)286 static void dict_reset(struct dictionary *dict, struct xz_buf *b)
287 {
288 if (DEC_IS_SINGLE(dict->mode)) {
289 dict->buf = b->out + b->out_pos;
290 dict->end = b->out_size - b->out_pos;
291 }
292
293 dict->start = 0;
294 dict->pos = 0;
295 dict->limit = 0;
296 dict->full = 0;
297 }
298
299 /* Set dictionary write limit */
dict_limit(struct dictionary * dict,size_t out_max)300 static void dict_limit(struct dictionary *dict, size_t out_max)
301 {
302 if (dict->end - dict->pos <= out_max)
303 dict->limit = dict->end;
304 else
305 dict->limit = dict->pos + out_max;
306 }
307
308 /* Return true if at least one byte can be written into the dictionary. */
dict_has_space(const struct dictionary * dict)309 static inline bool dict_has_space(const struct dictionary *dict)
310 {
311 return dict->pos < dict->limit;
312 }
313
314 /*
315 * Get a byte from the dictionary at the given distance. The distance is
316 * assumed to valid, or as a special case, zero when the dictionary is
317 * still empty. This special case is needed for single-call decoding to
318 * avoid writing a '\0' to the end of the destination buffer.
319 */
dict_get(const struct dictionary * dict,uint32_t dist)320 static inline uint32_t dict_get(const struct dictionary *dict, uint32_t dist)
321 {
322 size_t offset = dict->pos - dist - 1;
323
324 if (dist >= dict->pos)
325 offset += dict->end;
326
327 return dict->full > 0 ? dict->buf[offset] : 0;
328 }
329
330 /*
331 * Put one byte into the dictionary. It is assumed that there is space for it.
332 */
dict_put(struct dictionary * dict,uint8_t byte)333 static inline void dict_put(struct dictionary *dict, uint8_t byte)
334 {
335 dict->buf[dict->pos++] = byte;
336
337 if (dict->full < dict->pos)
338 dict->full = dict->pos;
339 }
340
341 /*
342 * Repeat given number of bytes from the given distance. If the distance is
343 * invalid, false is returned. On success, true is returned and *len is
344 * updated to indicate how many bytes were left to be repeated.
345 */
dict_repeat(struct dictionary * dict,uint32_t * len,uint32_t dist)346 static bool dict_repeat(struct dictionary *dict, uint32_t *len, uint32_t dist)
347 {
348 size_t back;
349 uint32_t left;
350
351 if (dist >= dict->full || dist >= dict->size)
352 return false;
353
354 left = min_t(size_t, dict->limit - dict->pos, *len);
355 *len -= left;
356
357 back = dict->pos - dist - 1;
358 if (dist >= dict->pos)
359 back += dict->end;
360
361 do {
362 dict->buf[dict->pos++] = dict->buf[back++];
363 if (back == dict->end)
364 back = 0;
365 } while (--left > 0);
366
367 if (dict->full < dict->pos)
368 dict->full = dict->pos;
369
370 return true;
371 }
372
373 /* Copy uncompressed data as is from input to dictionary and output buffers. */
dict_uncompressed(struct dictionary * dict,struct xz_buf * b,uint32_t * left)374 static void dict_uncompressed(struct dictionary *dict, struct xz_buf *b,
375 uint32_t *left)
376 {
377 size_t copy_size;
378
379 while (*left > 0 && b->in_pos < b->in_size
380 && b->out_pos < b->out_size) {
381 copy_size = min(b->in_size - b->in_pos,
382 b->out_size - b->out_pos);
383 if (copy_size > dict->end - dict->pos)
384 copy_size = dict->end - dict->pos;
385 if (copy_size > *left)
386 copy_size = *left;
387
388 *left -= copy_size;
389
390 memcpy(dict->buf + dict->pos, b->in + b->in_pos, copy_size);
391 dict->pos += copy_size;
392
393 if (dict->full < dict->pos)
394 dict->full = dict->pos;
395
396 if (DEC_IS_MULTI(dict->mode)) {
397 if (dict->pos == dict->end)
398 dict->pos = 0;
399
400 memcpy(b->out + b->out_pos, b->in + b->in_pos,
401 copy_size);
402 }
403
404 dict->start = dict->pos;
405
406 b->out_pos += copy_size;
407 b->in_pos += copy_size;
408 }
409 }
410
411 /*
412 * Flush pending data from dictionary to b->out. It is assumed that there is
413 * enough space in b->out. This is guaranteed because caller uses dict_limit()
414 * before decoding data into the dictionary.
415 */
dict_flush(struct dictionary * dict,struct xz_buf * b)416 static uint32_t dict_flush(struct dictionary *dict, struct xz_buf *b)
417 {
418 size_t copy_size = dict->pos - dict->start;
419
420 if (DEC_IS_MULTI(dict->mode)) {
421 if (dict->pos == dict->end)
422 dict->pos = 0;
423
424 memcpy(b->out + b->out_pos, dict->buf + dict->start,
425 copy_size);
426 }
427
428 dict->start = dict->pos;
429 b->out_pos += copy_size;
430 return copy_size;
431 }
432
433 /*****************
434 * Range decoder *
435 *****************/
436
437 /* Reset the range decoder. */
rc_reset(struct rc_dec * rc)438 static void rc_reset(struct rc_dec *rc)
439 {
440 rc->range = (uint32_t)-1;
441 rc->code = 0;
442 rc->init_bytes_left = RC_INIT_BYTES;
443 }
444
445 /*
446 * Read the first five initial bytes into rc->code if they haven't been
447 * read already. (Yes, the first byte gets completely ignored.)
448 */
rc_read_init(struct rc_dec * rc,struct xz_buf * b)449 static bool rc_read_init(struct rc_dec *rc, struct xz_buf *b)
450 {
451 while (rc->init_bytes_left > 0) {
452 if (b->in_pos == b->in_size)
453 return false;
454
455 rc->code = (rc->code << 8) + b->in[b->in_pos++];
456 --rc->init_bytes_left;
457 }
458
459 return true;
460 }
461
462 /* Return true if there may not be enough input for the next decoding loop. */
rc_limit_exceeded(const struct rc_dec * rc)463 static inline bool rc_limit_exceeded(const struct rc_dec *rc)
464 {
465 return rc->in_pos > rc->in_limit;
466 }
467
468 /*
469 * Return true if it is possible (from point of view of range decoder) that
470 * we have reached the end of the LZMA chunk.
471 */
rc_is_finished(const struct rc_dec * rc)472 static inline bool rc_is_finished(const struct rc_dec *rc)
473 {
474 return rc->code == 0;
475 }
476
477 /* Read the next input byte if needed. */
rc_normalize(struct rc_dec * rc)478 static __always_inline void rc_normalize(struct rc_dec *rc)
479 {
480 if (rc->range < RC_TOP_VALUE) {
481 rc->range <<= RC_SHIFT_BITS;
482 rc->code = (rc->code << RC_SHIFT_BITS) + rc->in[rc->in_pos++];
483 }
484 }
485
486 /*
487 * Decode one bit. In some versions, this function has been split in three
488 * functions so that the compiler is supposed to be able to more easily avoid
489 * an extra branch. In this particular version of the LZMA decoder, this
490 * doesn't seem to be a good idea (tested with GCC 3.3.6, 3.4.6, and 4.3.3
491 * on x86). Using a non-splitted version results in nicer looking code too.
492 *
493 * NOTE: This must return an int. Do not make it return a bool or the speed
494 * of the code generated by GCC 3.x decreases 10-15 %. (GCC 4.3 doesn't care,
495 * and it generates 10-20 % faster code than GCC 3.x from this file anyway.)
496 */
rc_bit(struct rc_dec * rc,uint16_t * prob)497 static __always_inline int rc_bit(struct rc_dec *rc, uint16_t *prob)
498 {
499 uint32_t bound;
500 int bit;
501
502 rc_normalize(rc);
503 bound = (rc->range >> RC_BIT_MODEL_TOTAL_BITS) * *prob;
504 if (rc->code < bound) {
505 rc->range = bound;
506 *prob += (RC_BIT_MODEL_TOTAL - *prob) >> RC_MOVE_BITS;
507 bit = 0;
508 } else {
509 rc->range -= bound;
510 rc->code -= bound;
511 *prob -= *prob >> RC_MOVE_BITS;
512 bit = 1;
513 }
514
515 return bit;
516 }
517
518 /* Decode a bittree starting from the most significant bit. */
rc_bittree(struct rc_dec * rc,uint16_t * probs,uint32_t limit)519 static __always_inline uint32_t rc_bittree(struct rc_dec *rc,
520 uint16_t *probs, uint32_t limit)
521 {
522 uint32_t symbol = 1;
523
524 do {
525 if (rc_bit(rc, &probs[symbol]))
526 symbol = (symbol << 1) + 1;
527 else
528 symbol <<= 1;
529 } while (symbol < limit);
530
531 return symbol;
532 }
533
534 /* 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)535 static __always_inline void rc_bittree_reverse(struct rc_dec *rc,
536 uint16_t *probs,
537 uint32_t *dest, uint32_t limit)
538 {
539 uint32_t symbol = 1;
540 uint32_t i = 0;
541
542 do {
543 if (rc_bit(rc, &probs[symbol])) {
544 symbol = (symbol << 1) + 1;
545 *dest += 1 << i;
546 } else {
547 symbol <<= 1;
548 }
549 } while (++i < limit);
550 }
551
552 /* Decode direct bits (fixed fifty-fifty probability) */
rc_direct(struct rc_dec * rc,uint32_t * dest,uint32_t limit)553 static inline void rc_direct(struct rc_dec *rc, uint32_t *dest, uint32_t limit)
554 {
555 uint32_t mask;
556
557 do {
558 rc_normalize(rc);
559 rc->range >>= 1;
560 rc->code -= rc->range;
561 mask = (uint32_t)0 - (rc->code >> 31);
562 rc->code += rc->range & mask;
563 *dest = (*dest << 1) + (mask + 1);
564 } while (--limit > 0);
565 }
566
567 /********
568 * LZMA *
569 ********/
570
571 /* Get pointer to literal coder probability array. */
lzma_literal_probs(struct xz_dec_lzma2 * s)572 static uint16_t *lzma_literal_probs(struct xz_dec_lzma2 *s)
573 {
574 uint32_t prev_byte = dict_get(&s->dict, 0);
575 uint32_t low = prev_byte >> (8 - s->lzma.lc);
576 uint32_t high = (s->dict.pos & s->lzma.literal_pos_mask) << s->lzma.lc;
577 return s->lzma.literal[low + high];
578 }
579
580 /* Decode a literal (one 8-bit byte) */
lzma_literal(struct xz_dec_lzma2 * s)581 static void lzma_literal(struct xz_dec_lzma2 *s)
582 {
583 uint16_t *probs;
584 uint32_t symbol;
585 uint32_t match_byte;
586 uint32_t match_bit;
587 uint32_t offset;
588 uint32_t i;
589
590 probs = lzma_literal_probs(s);
591
592 if (lzma_state_is_literal(s->lzma.state)) {
593 symbol = rc_bittree(&s->rc, probs, 0x100);
594 } else {
595 symbol = 1;
596 match_byte = dict_get(&s->dict, s->lzma.rep0) << 1;
597 offset = 0x100;
598
599 do {
600 match_bit = match_byte & offset;
601 match_byte <<= 1;
602 i = offset + match_bit + symbol;
603
604 if (rc_bit(&s->rc, &probs[i])) {
605 symbol = (symbol << 1) + 1;
606 offset &= match_bit;
607 } else {
608 symbol <<= 1;
609 offset &= ~match_bit;
610 }
611 } while (symbol < 0x100);
612 }
613
614 dict_put(&s->dict, (uint8_t)symbol);
615 lzma_state_literal(&s->lzma.state);
616 }
617
618 /* 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)619 static void lzma_len(struct xz_dec_lzma2 *s, struct lzma_len_dec *l,
620 uint32_t pos_state)
621 {
622 uint16_t *probs;
623 uint32_t limit;
624
625 if (!rc_bit(&s->rc, &l->choice)) {
626 probs = l->low[pos_state];
627 limit = LEN_LOW_SYMBOLS;
628 s->lzma.len = MATCH_LEN_MIN;
629 } else {
630 if (!rc_bit(&s->rc, &l->choice2)) {
631 probs = l->mid[pos_state];
632 limit = LEN_MID_SYMBOLS;
633 s->lzma.len = MATCH_LEN_MIN + LEN_LOW_SYMBOLS;
634 } else {
635 probs = l->high;
636 limit = LEN_HIGH_SYMBOLS;
637 s->lzma.len = MATCH_LEN_MIN + LEN_LOW_SYMBOLS
638 + LEN_MID_SYMBOLS;
639 }
640 }
641
642 s->lzma.len += rc_bittree(&s->rc, probs, limit) - limit;
643 }
644
645 /* Decode a match. The distance will be stored in s->lzma.rep0. */
lzma_match(struct xz_dec_lzma2 * s,uint32_t pos_state)646 static void lzma_match(struct xz_dec_lzma2 *s, uint32_t pos_state)
647 {
648 uint16_t *probs;
649 uint32_t dist_slot;
650 uint32_t limit;
651
652 lzma_state_match(&s->lzma.state);
653
654 s->lzma.rep3 = s->lzma.rep2;
655 s->lzma.rep2 = s->lzma.rep1;
656 s->lzma.rep1 = s->lzma.rep0;
657
658 lzma_len(s, &s->lzma.match_len_dec, pos_state);
659
660 probs = s->lzma.dist_slot[lzma_get_dist_state(s->lzma.len)];
661 dist_slot = rc_bittree(&s->rc, probs, DIST_SLOTS) - DIST_SLOTS;
662
663 if (dist_slot < DIST_MODEL_START) {
664 s->lzma.rep0 = dist_slot;
665 } else {
666 limit = (dist_slot >> 1) - 1;
667 s->lzma.rep0 = 2 + (dist_slot & 1);
668
669 if (dist_slot < DIST_MODEL_END) {
670 s->lzma.rep0 <<= limit;
671 probs = s->lzma.dist_special + s->lzma.rep0
672 - dist_slot - 1;
673 rc_bittree_reverse(&s->rc, probs,
674 &s->lzma.rep0, limit);
675 } else {
676 rc_direct(&s->rc, &s->lzma.rep0, limit - ALIGN_BITS);
677 s->lzma.rep0 <<= ALIGN_BITS;
678 rc_bittree_reverse(&s->rc, s->lzma.dist_align,
679 &s->lzma.rep0, ALIGN_BITS);
680 }
681 }
682 }
683
684 /*
685 * Decode a repeated match. The distance is one of the four most recently
686 * seen matches. The distance will be stored in s->lzma.rep0.
687 */
lzma_rep_match(struct xz_dec_lzma2 * s,uint32_t pos_state)688 static void lzma_rep_match(struct xz_dec_lzma2 *s, uint32_t pos_state)
689 {
690 uint32_t tmp;
691
692 if (!rc_bit(&s->rc, &s->lzma.is_rep0[s->lzma.state])) {
693 if (!rc_bit(&s->rc, &s->lzma.is_rep0_long[
694 s->lzma.state][pos_state])) {
695 lzma_state_short_rep(&s->lzma.state);
696 s->lzma.len = 1;
697 return;
698 }
699 } else {
700 if (!rc_bit(&s->rc, &s->lzma.is_rep1[s->lzma.state])) {
701 tmp = s->lzma.rep1;
702 } else {
703 if (!rc_bit(&s->rc, &s->lzma.is_rep2[s->lzma.state])) {
704 tmp = s->lzma.rep2;
705 } else {
706 tmp = s->lzma.rep3;
707 s->lzma.rep3 = s->lzma.rep2;
708 }
709
710 s->lzma.rep2 = s->lzma.rep1;
711 }
712
713 s->lzma.rep1 = s->lzma.rep0;
714 s->lzma.rep0 = tmp;
715 }
716
717 lzma_state_long_rep(&s->lzma.state);
718 lzma_len(s, &s->lzma.rep_len_dec, pos_state);
719 }
720
721 /* LZMA decoder core */
lzma_main(struct xz_dec_lzma2 * s)722 static bool lzma_main(struct xz_dec_lzma2 *s)
723 {
724 uint32_t pos_state;
725
726 /*
727 * If the dictionary was reached during the previous call, try to
728 * finish the possibly pending repeat in the dictionary.
729 */
730 if (dict_has_space(&s->dict) && s->lzma.len > 0)
731 dict_repeat(&s->dict, &s->lzma.len, s->lzma.rep0);
732
733 /*
734 * Decode more LZMA symbols. One iteration may consume up to
735 * LZMA_IN_REQUIRED - 1 bytes.
736 */
737 while (dict_has_space(&s->dict) && !rc_limit_exceeded(&s->rc)) {
738 pos_state = s->dict.pos & s->lzma.pos_mask;
739
740 if (!rc_bit(&s->rc, &s->lzma.is_match[
741 s->lzma.state][pos_state])) {
742 lzma_literal(s);
743 } else {
744 if (rc_bit(&s->rc, &s->lzma.is_rep[s->lzma.state]))
745 lzma_rep_match(s, pos_state);
746 else
747 lzma_match(s, pos_state);
748
749 if (!dict_repeat(&s->dict, &s->lzma.len, s->lzma.rep0))
750 return false;
751 }
752 }
753
754 /*
755 * Having the range decoder always normalized when we are outside
756 * this function makes it easier to correctly handle end of the chunk.
757 */
758 rc_normalize(&s->rc);
759
760 return true;
761 }
762
763 /*
764 * Reset the LZMA decoder and range decoder state. Dictionary is not reset
765 * here, because LZMA state may be reset without resetting the dictionary.
766 */
lzma_reset(struct xz_dec_lzma2 * s)767 static void lzma_reset(struct xz_dec_lzma2 *s)
768 {
769 uint16_t *probs;
770 size_t i;
771
772 s->lzma.state = STATE_LIT_LIT;
773 s->lzma.rep0 = 0;
774 s->lzma.rep1 = 0;
775 s->lzma.rep2 = 0;
776 s->lzma.rep3 = 0;
777
778 /*
779 * All probabilities are initialized to the same value. This hack
780 * makes the code smaller by avoiding a separate loop for each
781 * probability array.
782 *
783 * This could be optimized so that only that part of literal
784 * probabilities that are actually required. In the common case
785 * we would write 12 KiB less.
786 */
787 probs = s->lzma.is_match[0];
788 for (i = 0; i < PROBS_TOTAL; ++i)
789 probs[i] = RC_BIT_MODEL_TOTAL / 2;
790
791 rc_reset(&s->rc);
792 }
793
794 /*
795 * Decode and validate LZMA properties (lc/lp/pb) and calculate the bit masks
796 * from the decoded lp and pb values. On success, the LZMA decoder state is
797 * reset and true is returned.
798 */
lzma_props(struct xz_dec_lzma2 * s,uint8_t props)799 static bool lzma_props(struct xz_dec_lzma2 *s, uint8_t props)
800 {
801 if (props > (4 * 5 + 4) * 9 + 8)
802 return false;
803
804 s->lzma.pos_mask = 0;
805 while (props >= 9 * 5) {
806 props -= 9 * 5;
807 ++s->lzma.pos_mask;
808 }
809
810 s->lzma.pos_mask = (1 << s->lzma.pos_mask) - 1;
811
812 s->lzma.literal_pos_mask = 0;
813 while (props >= 9) {
814 props -= 9;
815 ++s->lzma.literal_pos_mask;
816 }
817
818 s->lzma.lc = props;
819
820 if (s->lzma.lc + s->lzma.literal_pos_mask > 4)
821 return false;
822
823 s->lzma.literal_pos_mask = (1 << s->lzma.literal_pos_mask) - 1;
824
825 lzma_reset(s);
826
827 return true;
828 }
829
830 /*********
831 * LZMA2 *
832 *********/
833
834 /*
835 * The LZMA decoder assumes that if the input limit (s->rc.in_limit) hasn't
836 * been exceeded, it is safe to read up to LZMA_IN_REQUIRED bytes. This
837 * wrapper function takes care of making the LZMA decoder's assumption safe.
838 *
839 * As long as there is plenty of input left to be decoded in the current LZMA
840 * chunk, we decode directly from the caller-supplied input buffer until
841 * there's LZMA_IN_REQUIRED bytes left. Those remaining bytes are copied into
842 * s->temp.buf, which (hopefully) gets filled on the next call to this
843 * function. We decode a few bytes from the temporary buffer so that we can
844 * continue decoding from the caller-supplied input buffer again.
845 */
lzma2_lzma(struct xz_dec_lzma2 * s,struct xz_buf * b)846 static bool lzma2_lzma(struct xz_dec_lzma2 *s, struct xz_buf *b)
847 {
848 size_t in_avail;
849 uint32_t tmp;
850
851 in_avail = b->in_size - b->in_pos;
852 if (s->temp.size > 0 || s->lzma2.compressed == 0) {
853 tmp = 2 * LZMA_IN_REQUIRED - s->temp.size;
854 if (tmp > s->lzma2.compressed - s->temp.size)
855 tmp = s->lzma2.compressed - s->temp.size;
856 if (tmp > in_avail)
857 tmp = in_avail;
858
859 memcpy(s->temp.buf + s->temp.size, b->in + b->in_pos, tmp);
860
861 if (s->temp.size + tmp == s->lzma2.compressed) {
862 memzero(s->temp.buf + s->temp.size + tmp,
863 sizeof(s->temp.buf)
864 - s->temp.size - tmp);
865 s->rc.in_limit = s->temp.size + tmp;
866 } else if (s->temp.size + tmp < LZMA_IN_REQUIRED) {
867 s->temp.size += tmp;
868 b->in_pos += tmp;
869 return true;
870 } else {
871 s->rc.in_limit = s->temp.size + tmp - LZMA_IN_REQUIRED;
872 }
873
874 s->rc.in = s->temp.buf;
875 s->rc.in_pos = 0;
876
877 if (!lzma_main(s) || s->rc.in_pos > s->temp.size + tmp)
878 return false;
879
880 s->lzma2.compressed -= s->rc.in_pos;
881
882 if (s->rc.in_pos < s->temp.size) {
883 s->temp.size -= s->rc.in_pos;
884 memmove(s->temp.buf, s->temp.buf + s->rc.in_pos,
885 s->temp.size);
886 return true;
887 }
888
889 b->in_pos += s->rc.in_pos - s->temp.size;
890 s->temp.size = 0;
891 }
892
893 in_avail = b->in_size - b->in_pos;
894 if (in_avail >= LZMA_IN_REQUIRED) {
895 s->rc.in = b->in;
896 s->rc.in_pos = b->in_pos;
897
898 if (in_avail >= s->lzma2.compressed + LZMA_IN_REQUIRED)
899 s->rc.in_limit = b->in_pos + s->lzma2.compressed;
900 else
901 s->rc.in_limit = b->in_size - LZMA_IN_REQUIRED;
902
903 if (!lzma_main(s))
904 return false;
905
906 in_avail = s->rc.in_pos - b->in_pos;
907 if (in_avail > s->lzma2.compressed)
908 return false;
909
910 s->lzma2.compressed -= in_avail;
911 b->in_pos = s->rc.in_pos;
912 }
913
914 in_avail = b->in_size - b->in_pos;
915 if (in_avail < LZMA_IN_REQUIRED) {
916 if (in_avail > s->lzma2.compressed)
917 in_avail = s->lzma2.compressed;
918
919 memcpy(s->temp.buf, b->in + b->in_pos, in_avail);
920 s->temp.size = in_avail;
921 b->in_pos += in_avail;
922 }
923
924 return true;
925 }
926
927 /*
928 * Take care of the LZMA2 control layer, and forward the job of actual LZMA
929 * decoding or copying of uncompressed chunks to other functions.
930 */
xz_dec_lzma2_run(struct xz_dec_lzma2 * s,struct xz_buf * b)931 XZ_EXTERN enum xz_ret xz_dec_lzma2_run(struct xz_dec_lzma2 *s,
932 struct xz_buf *b)
933 {
934 uint32_t tmp;
935
936 while (b->in_pos < b->in_size || s->lzma2.sequence == SEQ_LZMA_RUN) {
937 switch (s->lzma2.sequence) {
938 case SEQ_CONTROL:
939 /*
940 * LZMA2 control byte
941 *
942 * Exact values:
943 * 0x00 End marker
944 * 0x01 Dictionary reset followed by
945 * an uncompressed chunk
946 * 0x02 Uncompressed chunk (no dictionary reset)
947 *
948 * Highest three bits (s->control & 0xE0):
949 * 0xE0 Dictionary reset, new properties and state
950 * reset, followed by LZMA compressed chunk
951 * 0xC0 New properties and state reset, followed
952 * by LZMA compressed chunk (no dictionary
953 * reset)
954 * 0xA0 State reset using old properties,
955 * followed by LZMA compressed chunk (no
956 * dictionary reset)
957 * 0x80 LZMA chunk (no dictionary or state reset)
958 *
959 * For LZMA compressed chunks, the lowest five bits
960 * (s->control & 1F) are the highest bits of the
961 * uncompressed size (bits 16-20).
962 *
963 * A new LZMA2 stream must begin with a dictionary
964 * reset. The first LZMA chunk must set new
965 * properties and reset the LZMA state.
966 *
967 * Values that don't match anything described above
968 * are invalid and we return XZ_DATA_ERROR.
969 */
970 tmp = b->in[b->in_pos++];
971
972 if (tmp == 0x00)
973 return XZ_STREAM_END;
974
975 if (tmp >= 0xE0 || tmp == 0x01) {
976 s->lzma2.need_props = true;
977 s->lzma2.need_dict_reset = false;
978 dict_reset(&s->dict, b);
979 } else if (s->lzma2.need_dict_reset) {
980 return XZ_DATA_ERROR;
981 }
982
983 if (tmp >= 0x80) {
984 s->lzma2.uncompressed = (tmp & 0x1F) << 16;
985 s->lzma2.sequence = SEQ_UNCOMPRESSED_1;
986
987 if (tmp >= 0xC0) {
988 /*
989 * When there are new properties,
990 * state reset is done at
991 * SEQ_PROPERTIES.
992 */
993 s->lzma2.need_props = false;
994 s->lzma2.next_sequence
995 = SEQ_PROPERTIES;
996
997 } else if (s->lzma2.need_props) {
998 return XZ_DATA_ERROR;
999
1000 } else {
1001 s->lzma2.next_sequence
1002 = SEQ_LZMA_PREPARE;
1003 if (tmp >= 0xA0)
1004 lzma_reset(s);
1005 }
1006 } else {
1007 if (tmp > 0x02)
1008 return XZ_DATA_ERROR;
1009
1010 s->lzma2.sequence = SEQ_COMPRESSED_0;
1011 s->lzma2.next_sequence = SEQ_COPY;
1012 }
1013
1014 break;
1015
1016 case SEQ_UNCOMPRESSED_1:
1017 s->lzma2.uncompressed
1018 += (uint32_t)b->in[b->in_pos++] << 8;
1019 s->lzma2.sequence = SEQ_UNCOMPRESSED_2;
1020 break;
1021
1022 case SEQ_UNCOMPRESSED_2:
1023 s->lzma2.uncompressed
1024 += (uint32_t)b->in[b->in_pos++] + 1;
1025 s->lzma2.sequence = SEQ_COMPRESSED_0;
1026 break;
1027
1028 case SEQ_COMPRESSED_0:
1029 s->lzma2.compressed
1030 = (uint32_t)b->in[b->in_pos++] << 8;
1031 s->lzma2.sequence = SEQ_COMPRESSED_1;
1032 break;
1033
1034 case SEQ_COMPRESSED_1:
1035 s->lzma2.compressed
1036 += (uint32_t)b->in[b->in_pos++] + 1;
1037 s->lzma2.sequence = s->lzma2.next_sequence;
1038 break;
1039
1040 case SEQ_PROPERTIES:
1041 if (!lzma_props(s, b->in[b->in_pos++]))
1042 return XZ_DATA_ERROR;
1043
1044 s->lzma2.sequence = SEQ_LZMA_PREPARE;
1045
1046 fallthrough;
1047
1048 case SEQ_LZMA_PREPARE:
1049 if (s->lzma2.compressed < RC_INIT_BYTES)
1050 return XZ_DATA_ERROR;
1051
1052 if (!rc_read_init(&s->rc, b))
1053 return XZ_OK;
1054
1055 s->lzma2.compressed -= RC_INIT_BYTES;
1056 s->lzma2.sequence = SEQ_LZMA_RUN;
1057
1058 fallthrough;
1059
1060 case SEQ_LZMA_RUN:
1061 /*
1062 * Set dictionary limit to indicate how much we want
1063 * to be encoded at maximum. Decode new data into the
1064 * dictionary. Flush the new data from dictionary to
1065 * b->out. Check if we finished decoding this chunk.
1066 * In case the dictionary got full but we didn't fill
1067 * the output buffer yet, we may run this loop
1068 * multiple times without changing s->lzma2.sequence.
1069 */
1070 dict_limit(&s->dict, min_t(size_t,
1071 b->out_size - b->out_pos,
1072 s->lzma2.uncompressed));
1073 if (!lzma2_lzma(s, b))
1074 return XZ_DATA_ERROR;
1075
1076 s->lzma2.uncompressed -= dict_flush(&s->dict, b);
1077
1078 if (s->lzma2.uncompressed == 0) {
1079 if (s->lzma2.compressed > 0 || s->lzma.len > 0
1080 || !rc_is_finished(&s->rc))
1081 return XZ_DATA_ERROR;
1082
1083 rc_reset(&s->rc);
1084 s->lzma2.sequence = SEQ_CONTROL;
1085
1086 } else if (b->out_pos == b->out_size
1087 || (b->in_pos == b->in_size
1088 && s->temp.size
1089 < s->lzma2.compressed)) {
1090 return XZ_OK;
1091 }
1092
1093 break;
1094
1095 case SEQ_COPY:
1096 dict_uncompressed(&s->dict, b, &s->lzma2.compressed);
1097 if (s->lzma2.compressed > 0)
1098 return XZ_OK;
1099
1100 s->lzma2.sequence = SEQ_CONTROL;
1101 break;
1102 }
1103 }
1104
1105 return XZ_OK;
1106 }
1107
xz_dec_lzma2_create(enum xz_mode mode,uint32_t dict_max)1108 XZ_EXTERN struct xz_dec_lzma2 *xz_dec_lzma2_create(enum xz_mode mode,
1109 uint32_t dict_max)
1110 {
1111 struct xz_dec_lzma2 *s = kmalloc(sizeof(*s), GFP_KERNEL);
1112 if (s == NULL)
1113 return NULL;
1114
1115 s->dict.mode = mode;
1116 s->dict.size_max = dict_max;
1117
1118 if (DEC_IS_PREALLOC(mode)) {
1119 s->dict.buf = vmalloc(dict_max);
1120 if (s->dict.buf == NULL) {
1121 kfree(s);
1122 return NULL;
1123 }
1124 } else if (DEC_IS_DYNALLOC(mode)) {
1125 s->dict.buf = NULL;
1126 s->dict.allocated = 0;
1127 }
1128
1129 return s;
1130 }
1131
xz_dec_lzma2_reset(struct xz_dec_lzma2 * s,uint8_t props)1132 XZ_EXTERN enum xz_ret xz_dec_lzma2_reset(struct xz_dec_lzma2 *s, uint8_t props)
1133 {
1134 /* This limits dictionary size to 3 GiB to keep parsing simpler. */
1135 if (props > 39)
1136 return XZ_OPTIONS_ERROR;
1137
1138 s->dict.size = 2 + (props & 1);
1139 s->dict.size <<= (props >> 1) + 11;
1140
1141 if (DEC_IS_MULTI(s->dict.mode)) {
1142 if (s->dict.size > s->dict.size_max)
1143 return XZ_MEMLIMIT_ERROR;
1144
1145 s->dict.end = s->dict.size;
1146
1147 if (DEC_IS_DYNALLOC(s->dict.mode)) {
1148 if (s->dict.allocated < s->dict.size) {
1149 s->dict.allocated = s->dict.size;
1150 vfree(s->dict.buf);
1151 s->dict.buf = vmalloc(s->dict.size);
1152 if (s->dict.buf == NULL) {
1153 s->dict.allocated = 0;
1154 return XZ_MEM_ERROR;
1155 }
1156 }
1157 }
1158 }
1159
1160 s->lzma.len = 0;
1161
1162 s->lzma2.sequence = SEQ_CONTROL;
1163 s->lzma2.need_dict_reset = true;
1164
1165 s->temp.size = 0;
1166
1167 return XZ_OK;
1168 }
1169
xz_dec_lzma2_end(struct xz_dec_lzma2 * s)1170 XZ_EXTERN void xz_dec_lzma2_end(struct xz_dec_lzma2 *s)
1171 {
1172 if (DEC_IS_MULTI(s->dict.mode))
1173 vfree(s->dict.buf);
1174
1175 kfree(s);
1176 }
1177
