1 /*
2 * LZMA2 decoder
3 *
4 * Authors: Lasse Collin <lasse.collin@tukaani.org>
5 * Igor Pavlov <http://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 dervied from the number of literal
151 * position bits, and a mask dervied 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 /*
391 * If doing in-place decompression in single-call mode and the
392 * uncompressed size of the file is larger than the caller
393 * thought (i.e. it is invalid input!), the buffers below may
394 * overlap and cause undefined behavior with memcpy().
395 * With valid inputs memcpy() would be fine here.
396 */
397 memmove(dict->buf + dict->pos, b->in + b->in_pos, copy_size);
398 dict->pos += copy_size;
399
400 if (dict->full < dict->pos)
401 dict->full = dict->pos;
402
403 if (DEC_IS_MULTI(dict->mode)) {
404 if (dict->pos == dict->end)
405 dict->pos = 0;
406
407 /*
408 * Like above but for multi-call mode: use memmove()
409 * to avoid undefined behavior with invalid input.
410 */
411 memmove(b->out + b->out_pos, b->in + b->in_pos,
412 copy_size);
413 }
414
415 dict->start = dict->pos;
416
417 b->out_pos += copy_size;
418 b->in_pos += copy_size;
419 }
420 }
421
422 /*
423 * Flush pending data from dictionary to b->out. It is assumed that there is
424 * enough space in b->out. This is guaranteed because caller uses dict_limit()
425 * before decoding data into the dictionary.
426 */
dict_flush(struct dictionary * dict,struct xz_buf * b)427 static uint32_t dict_flush(struct dictionary *dict, struct xz_buf *b)
428 {
429 size_t copy_size = dict->pos - dict->start;
430
431 if (DEC_IS_MULTI(dict->mode)) {
432 if (dict->pos == dict->end)
433 dict->pos = 0;
434
435 /*
436 * These buffers cannot overlap even if doing in-place
437 * decompression because in multi-call mode dict->buf
438 * has been allocated by us in this file; it's not
439 * provided by the caller like in single-call mode.
440 */
441 memcpy(b->out + b->out_pos, dict->buf + dict->start,
442 copy_size);
443 }
444
445 dict->start = dict->pos;
446 b->out_pos += copy_size;
447 return copy_size;
448 }
449
450 /*****************
451 * Range decoder *
452 *****************/
453
454 /* Reset the range decoder. */
rc_reset(struct rc_dec * rc)455 static void rc_reset(struct rc_dec *rc)
456 {
457 rc->range = (uint32_t)-1;
458 rc->code = 0;
459 rc->init_bytes_left = RC_INIT_BYTES;
460 }
461
462 /*
463 * Read the first five initial bytes into rc->code if they haven't been
464 * read already. (Yes, the first byte gets completely ignored.)
465 */
rc_read_init(struct rc_dec * rc,struct xz_buf * b)466 static bool rc_read_init(struct rc_dec *rc, struct xz_buf *b)
467 {
468 while (rc->init_bytes_left > 0) {
469 if (b->in_pos == b->in_size)
470 return false;
471
472 rc->code = (rc->code << 8) + b->in[b->in_pos++];
473 --rc->init_bytes_left;
474 }
475
476 return true;
477 }
478
479 /* Return true if there may not be enough input for the next decoding loop. */
rc_limit_exceeded(const struct rc_dec * rc)480 static inline bool rc_limit_exceeded(const struct rc_dec *rc)
481 {
482 return rc->in_pos > rc->in_limit;
483 }
484
485 /*
486 * Return true if it is possible (from point of view of range decoder) that
487 * we have reached the end of the LZMA chunk.
488 */
rc_is_finished(const struct rc_dec * rc)489 static inline bool rc_is_finished(const struct rc_dec *rc)
490 {
491 return rc->code == 0;
492 }
493
494 /* Read the next input byte if needed. */
rc_normalize(struct rc_dec * rc)495 static __always_inline void rc_normalize(struct rc_dec *rc)
496 {
497 if (rc->range < RC_TOP_VALUE) {
498 rc->range <<= RC_SHIFT_BITS;
499 rc->code = (rc->code << RC_SHIFT_BITS) + rc->in[rc->in_pos++];
500 }
501 }
502
503 /*
504 * Decode one bit. In some versions, this function has been splitted in three
505 * functions so that the compiler is supposed to be able to more easily avoid
506 * an extra branch. In this particular version of the LZMA decoder, this
507 * doesn't seem to be a good idea (tested with GCC 3.3.6, 3.4.6, and 4.3.3
508 * on x86). Using a non-splitted version results in nicer looking code too.
509 *
510 * NOTE: This must return an int. Do not make it return a bool or the speed
511 * of the code generated by GCC 3.x decreases 10-15 %. (GCC 4.3 doesn't care,
512 * and it generates 10-20 % faster code than GCC 3.x from this file anyway.)
513 */
rc_bit(struct rc_dec * rc,uint16_t * prob)514 static __always_inline int rc_bit(struct rc_dec *rc, uint16_t *prob)
515 {
516 uint32_t bound;
517 int bit;
518
519 rc_normalize(rc);
520 bound = (rc->range >> RC_BIT_MODEL_TOTAL_BITS) * *prob;
521 if (rc->code < bound) {
522 rc->range = bound;
523 *prob += (RC_BIT_MODEL_TOTAL - *prob) >> RC_MOVE_BITS;
524 bit = 0;
525 } else {
526 rc->range -= bound;
527 rc->code -= bound;
528 *prob -= *prob >> RC_MOVE_BITS;
529 bit = 1;
530 }
531
532 return bit;
533 }
534
535 /* Decode a bittree starting from the most significant bit. */
rc_bittree(struct rc_dec * rc,uint16_t * probs,uint32_t limit)536 static __always_inline uint32_t rc_bittree(struct rc_dec *rc,
537 uint16_t *probs, uint32_t limit)
538 {
539 uint32_t symbol = 1;
540
541 do {
542 if (rc_bit(rc, &probs[symbol]))
543 symbol = (symbol << 1) + 1;
544 else
545 symbol <<= 1;
546 } while (symbol < limit);
547
548 return symbol;
549 }
550
551 /* 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)552 static __always_inline void rc_bittree_reverse(struct rc_dec *rc,
553 uint16_t *probs,
554 uint32_t *dest, uint32_t limit)
555 {
556 uint32_t symbol = 1;
557 uint32_t i = 0;
558
559 do {
560 if (rc_bit(rc, &probs[symbol])) {
561 symbol = (symbol << 1) + 1;
562 *dest += 1 << i;
563 } else {
564 symbol <<= 1;
565 }
566 } while (++i < limit);
567 }
568
569 /* Decode direct bits (fixed fifty-fifty probability) */
rc_direct(struct rc_dec * rc,uint32_t * dest,uint32_t limit)570 static inline void rc_direct(struct rc_dec *rc, uint32_t *dest, uint32_t limit)
571 {
572 uint32_t mask;
573
574 do {
575 rc_normalize(rc);
576 rc->range >>= 1;
577 rc->code -= rc->range;
578 mask = (uint32_t)0 - (rc->code >> 31);
579 rc->code += rc->range & mask;
580 *dest = (*dest << 1) + (mask + 1);
581 } while (--limit > 0);
582 }
583
584 /********
585 * LZMA *
586 ********/
587
588 /* Get pointer to literal coder probability array. */
lzma_literal_probs(struct xz_dec_lzma2 * s)589 static uint16_t *lzma_literal_probs(struct xz_dec_lzma2 *s)
590 {
591 uint32_t prev_byte = dict_get(&s->dict, 0);
592 uint32_t low = prev_byte >> (8 - s->lzma.lc);
593 uint32_t high = (s->dict.pos & s->lzma.literal_pos_mask) << s->lzma.lc;
594 return s->lzma.literal[low + high];
595 }
596
597 /* Decode a literal (one 8-bit byte) */
lzma_literal(struct xz_dec_lzma2 * s)598 static void lzma_literal(struct xz_dec_lzma2 *s)
599 {
600 uint16_t *probs;
601 uint32_t symbol;
602 uint32_t match_byte;
603 uint32_t match_bit;
604 uint32_t offset;
605 uint32_t i;
606
607 probs = lzma_literal_probs(s);
608
609 if (lzma_state_is_literal(s->lzma.state)) {
610 symbol = rc_bittree(&s->rc, probs, 0x100);
611 } else {
612 symbol = 1;
613 match_byte = dict_get(&s->dict, s->lzma.rep0) << 1;
614 offset = 0x100;
615
616 do {
617 match_bit = match_byte & offset;
618 match_byte <<= 1;
619 i = offset + match_bit + symbol;
620
621 if (rc_bit(&s->rc, &probs[i])) {
622 symbol = (symbol << 1) + 1;
623 offset &= match_bit;
624 } else {
625 symbol <<= 1;
626 offset &= ~match_bit;
627 }
628 } while (symbol < 0x100);
629 }
630
631 dict_put(&s->dict, (uint8_t)symbol);
632 lzma_state_literal(&s->lzma.state);
633 }
634
635 /* 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)636 static void lzma_len(struct xz_dec_lzma2 *s, struct lzma_len_dec *l,
637 uint32_t pos_state)
638 {
639 uint16_t *probs;
640 uint32_t limit;
641
642 if (!rc_bit(&s->rc, &l->choice)) {
643 probs = l->low[pos_state];
644 limit = LEN_LOW_SYMBOLS;
645 s->lzma.len = MATCH_LEN_MIN;
646 } else {
647 if (!rc_bit(&s->rc, &l->choice2)) {
648 probs = l->mid[pos_state];
649 limit = LEN_MID_SYMBOLS;
650 s->lzma.len = MATCH_LEN_MIN + LEN_LOW_SYMBOLS;
651 } else {
652 probs = l->high;
653 limit = LEN_HIGH_SYMBOLS;
654 s->lzma.len = MATCH_LEN_MIN + LEN_LOW_SYMBOLS
655 + LEN_MID_SYMBOLS;
656 }
657 }
658
659 s->lzma.len += rc_bittree(&s->rc, probs, limit) - limit;
660 }
661
662 /* Decode a match. The distance will be stored in s->lzma.rep0. */
lzma_match(struct xz_dec_lzma2 * s,uint32_t pos_state)663 static void lzma_match(struct xz_dec_lzma2 *s, uint32_t pos_state)
664 {
665 uint16_t *probs;
666 uint32_t dist_slot;
667 uint32_t limit;
668
669 lzma_state_match(&s->lzma.state);
670
671 s->lzma.rep3 = s->lzma.rep2;
672 s->lzma.rep2 = s->lzma.rep1;
673 s->lzma.rep1 = s->lzma.rep0;
674
675 lzma_len(s, &s->lzma.match_len_dec, pos_state);
676
677 probs = s->lzma.dist_slot[lzma_get_dist_state(s->lzma.len)];
678 dist_slot = rc_bittree(&s->rc, probs, DIST_SLOTS) - DIST_SLOTS;
679
680 if (dist_slot < DIST_MODEL_START) {
681 s->lzma.rep0 = dist_slot;
682 } else {
683 limit = (dist_slot >> 1) - 1;
684 s->lzma.rep0 = 2 + (dist_slot & 1);
685
686 if (dist_slot < DIST_MODEL_END) {
687 s->lzma.rep0 <<= limit;
688 probs = s->lzma.dist_special + s->lzma.rep0
689 - dist_slot - 1;
690 rc_bittree_reverse(&s->rc, probs,
691 &s->lzma.rep0, limit);
692 } else {
693 rc_direct(&s->rc, &s->lzma.rep0, limit - ALIGN_BITS);
694 s->lzma.rep0 <<= ALIGN_BITS;
695 rc_bittree_reverse(&s->rc, s->lzma.dist_align,
696 &s->lzma.rep0, ALIGN_BITS);
697 }
698 }
699 }
700
701 /*
702 * Decode a repeated match. The distance is one of the four most recently
703 * seen matches. The distance will be stored in s->lzma.rep0.
704 */
lzma_rep_match(struct xz_dec_lzma2 * s,uint32_t pos_state)705 static void lzma_rep_match(struct xz_dec_lzma2 *s, uint32_t pos_state)
706 {
707 uint32_t tmp;
708
709 if (!rc_bit(&s->rc, &s->lzma.is_rep0[s->lzma.state])) {
710 if (!rc_bit(&s->rc, &s->lzma.is_rep0_long[
711 s->lzma.state][pos_state])) {
712 lzma_state_short_rep(&s->lzma.state);
713 s->lzma.len = 1;
714 return;
715 }
716 } else {
717 if (!rc_bit(&s->rc, &s->lzma.is_rep1[s->lzma.state])) {
718 tmp = s->lzma.rep1;
719 } else {
720 if (!rc_bit(&s->rc, &s->lzma.is_rep2[s->lzma.state])) {
721 tmp = s->lzma.rep2;
722 } else {
723 tmp = s->lzma.rep3;
724 s->lzma.rep3 = s->lzma.rep2;
725 }
726
727 s->lzma.rep2 = s->lzma.rep1;
728 }
729
730 s->lzma.rep1 = s->lzma.rep0;
731 s->lzma.rep0 = tmp;
732 }
733
734 lzma_state_long_rep(&s->lzma.state);
735 lzma_len(s, &s->lzma.rep_len_dec, pos_state);
736 }
737
738 /* LZMA decoder core */
lzma_main(struct xz_dec_lzma2 * s)739 static bool lzma_main(struct xz_dec_lzma2 *s)
740 {
741 uint32_t pos_state;
742
743 /*
744 * If the dictionary was reached during the previous call, try to
745 * finish the possibly pending repeat in the dictionary.
746 */
747 if (dict_has_space(&s->dict) && s->lzma.len > 0)
748 dict_repeat(&s->dict, &s->lzma.len, s->lzma.rep0);
749
750 /*
751 * Decode more LZMA symbols. One iteration may consume up to
752 * LZMA_IN_REQUIRED - 1 bytes.
753 */
754 while (dict_has_space(&s->dict) && !rc_limit_exceeded(&s->rc)) {
755 pos_state = s->dict.pos & s->lzma.pos_mask;
756
757 if (!rc_bit(&s->rc, &s->lzma.is_match[
758 s->lzma.state][pos_state])) {
759 lzma_literal(s);
760 } else {
761 if (rc_bit(&s->rc, &s->lzma.is_rep[s->lzma.state]))
762 lzma_rep_match(s, pos_state);
763 else
764 lzma_match(s, pos_state);
765
766 if (!dict_repeat(&s->dict, &s->lzma.len, s->lzma.rep0))
767 return false;
768 }
769 }
770
771 /*
772 * Having the range decoder always normalized when we are outside
773 * this function makes it easier to correctly handle end of the chunk.
774 */
775 rc_normalize(&s->rc);
776
777 return true;
778 }
779
780 /*
781 * Reset the LZMA decoder and range decoder state. Dictionary is nore reset
782 * here, because LZMA state may be reset without resetting the dictionary.
783 */
lzma_reset(struct xz_dec_lzma2 * s)784 static void lzma_reset(struct xz_dec_lzma2 *s)
785 {
786 uint16_t *probs;
787 size_t i;
788
789 s->lzma.state = STATE_LIT_LIT;
790 s->lzma.rep0 = 0;
791 s->lzma.rep1 = 0;
792 s->lzma.rep2 = 0;
793 s->lzma.rep3 = 0;
794
795 /*
796 * All probabilities are initialized to the same value. This hack
797 * makes the code smaller by avoiding a separate loop for each
798 * probability array.
799 *
800 * This could be optimized so that only that part of literal
801 * probabilities that are actually required. In the common case
802 * we would write 12 KiB less.
803 */
804 probs = s->lzma.is_match[0];
805 for (i = 0; i < PROBS_TOTAL; ++i)
806 probs[i] = RC_BIT_MODEL_TOTAL / 2;
807
808 rc_reset(&s->rc);
809 }
810
811 /*
812 * Decode and validate LZMA properties (lc/lp/pb) and calculate the bit masks
813 * from the decoded lp and pb values. On success, the LZMA decoder state is
814 * reset and true is returned.
815 */
lzma_props(struct xz_dec_lzma2 * s,uint8_t props)816 static bool lzma_props(struct xz_dec_lzma2 *s, uint8_t props)
817 {
818 if (props > (4 * 5 + 4) * 9 + 8)
819 return false;
820
821 s->lzma.pos_mask = 0;
822 while (props >= 9 * 5) {
823 props -= 9 * 5;
824 ++s->lzma.pos_mask;
825 }
826
827 s->lzma.pos_mask = (1 << s->lzma.pos_mask) - 1;
828
829 s->lzma.literal_pos_mask = 0;
830 while (props >= 9) {
831 props -= 9;
832 ++s->lzma.literal_pos_mask;
833 }
834
835 s->lzma.lc = props;
836
837 if (s->lzma.lc + s->lzma.literal_pos_mask > 4)
838 return false;
839
840 s->lzma.literal_pos_mask = (1 << s->lzma.literal_pos_mask) - 1;
841
842 lzma_reset(s);
843
844 return true;
845 }
846
847 /*********
848 * LZMA2 *
849 *********/
850
851 /*
852 * The LZMA decoder assumes that if the input limit (s->rc.in_limit) hasn't
853 * been exceeded, it is safe to read up to LZMA_IN_REQUIRED bytes. This
854 * wrapper function takes care of making the LZMA decoder's assumption safe.
855 *
856 * As long as there is plenty of input left to be decoded in the current LZMA
857 * chunk, we decode directly from the caller-supplied input buffer until
858 * there's LZMA_IN_REQUIRED bytes left. Those remaining bytes are copied into
859 * s->temp.buf, which (hopefully) gets filled on the next call to this
860 * function. We decode a few bytes from the temporary buffer so that we can
861 * continue decoding from the caller-supplied input buffer again.
862 */
lzma2_lzma(struct xz_dec_lzma2 * s,struct xz_buf * b)863 static bool lzma2_lzma(struct xz_dec_lzma2 *s, struct xz_buf *b)
864 {
865 size_t in_avail;
866 uint32_t tmp;
867
868 in_avail = b->in_size - b->in_pos;
869 if (s->temp.size > 0 || s->lzma2.compressed == 0) {
870 tmp = 2 * LZMA_IN_REQUIRED - s->temp.size;
871 if (tmp > s->lzma2.compressed - s->temp.size)
872 tmp = s->lzma2.compressed - s->temp.size;
873 if (tmp > in_avail)
874 tmp = in_avail;
875
876 memcpy(s->temp.buf + s->temp.size, b->in + b->in_pos, tmp);
877
878 if (s->temp.size + tmp == s->lzma2.compressed) {
879 memzero(s->temp.buf + s->temp.size + tmp,
880 sizeof(s->temp.buf)
881 - s->temp.size - tmp);
882 s->rc.in_limit = s->temp.size + tmp;
883 } else if (s->temp.size + tmp < LZMA_IN_REQUIRED) {
884 s->temp.size += tmp;
885 b->in_pos += tmp;
886 return true;
887 } else {
888 s->rc.in_limit = s->temp.size + tmp - LZMA_IN_REQUIRED;
889 }
890
891 s->rc.in = s->temp.buf;
892 s->rc.in_pos = 0;
893
894 if (!lzma_main(s) || s->rc.in_pos > s->temp.size + tmp)
895 return false;
896
897 s->lzma2.compressed -= s->rc.in_pos;
898
899 if (s->rc.in_pos < s->temp.size) {
900 s->temp.size -= s->rc.in_pos;
901 memmove(s->temp.buf, s->temp.buf + s->rc.in_pos,
902 s->temp.size);
903 return true;
904 }
905
906 b->in_pos += s->rc.in_pos - s->temp.size;
907 s->temp.size = 0;
908 }
909
910 in_avail = b->in_size - b->in_pos;
911 if (in_avail >= LZMA_IN_REQUIRED) {
912 s->rc.in = b->in;
913 s->rc.in_pos = b->in_pos;
914
915 if (in_avail >= s->lzma2.compressed + LZMA_IN_REQUIRED)
916 s->rc.in_limit = b->in_pos + s->lzma2.compressed;
917 else
918 s->rc.in_limit = b->in_size - LZMA_IN_REQUIRED;
919
920 if (!lzma_main(s))
921 return false;
922
923 in_avail = s->rc.in_pos - b->in_pos;
924 if (in_avail > s->lzma2.compressed)
925 return false;
926
927 s->lzma2.compressed -= in_avail;
928 b->in_pos = s->rc.in_pos;
929 }
930
931 in_avail = b->in_size - b->in_pos;
932 if (in_avail < LZMA_IN_REQUIRED) {
933 if (in_avail > s->lzma2.compressed)
934 in_avail = s->lzma2.compressed;
935
936 memcpy(s->temp.buf, b->in + b->in_pos, in_avail);
937 s->temp.size = in_avail;
938 b->in_pos += in_avail;
939 }
940
941 return true;
942 }
943
944 /*
945 * Take care of the LZMA2 control layer, and forward the job of actual LZMA
946 * decoding or copying of uncompressed chunks to other functions.
947 */
xz_dec_lzma2_run(struct xz_dec_lzma2 * s,struct xz_buf * b)948 XZ_EXTERN enum xz_ret xz_dec_lzma2_run(struct xz_dec_lzma2 *s,
949 struct xz_buf *b)
950 {
951 uint32_t tmp;
952
953 while (b->in_pos < b->in_size || s->lzma2.sequence == SEQ_LZMA_RUN) {
954 switch (s->lzma2.sequence) {
955 case SEQ_CONTROL:
956 /*
957 * LZMA2 control byte
958 *
959 * Exact values:
960 * 0x00 End marker
961 * 0x01 Dictionary reset followed by
962 * an uncompressed chunk
963 * 0x02 Uncompressed chunk (no dictionary reset)
964 *
965 * Highest three bits (s->control & 0xE0):
966 * 0xE0 Dictionary reset, new properties and state
967 * reset, followed by LZMA compressed chunk
968 * 0xC0 New properties and state reset, followed
969 * by LZMA compressed chunk (no dictionary
970 * reset)
971 * 0xA0 State reset using old properties,
972 * followed by LZMA compressed chunk (no
973 * dictionary reset)
974 * 0x80 LZMA chunk (no dictionary or state reset)
975 *
976 * For LZMA compressed chunks, the lowest five bits
977 * (s->control & 1F) are the highest bits of the
978 * uncompressed size (bits 16-20).
979 *
980 * A new LZMA2 stream must begin with a dictionary
981 * reset. The first LZMA chunk must set new
982 * properties and reset the LZMA state.
983 *
984 * Values that don't match anything described above
985 * are invalid and we return XZ_DATA_ERROR.
986 */
987 tmp = b->in[b->in_pos++];
988
989 if (tmp == 0x00)
990 return XZ_STREAM_END;
991
992 if (tmp >= 0xE0 || tmp == 0x01) {
993 s->lzma2.need_props = true;
994 s->lzma2.need_dict_reset = false;
995 dict_reset(&s->dict, b);
996 } else if (s->lzma2.need_dict_reset) {
997 return XZ_DATA_ERROR;
998 }
999
1000 if (tmp >= 0x80) {
1001 s->lzma2.uncompressed = (tmp & 0x1F) << 16;
1002 s->lzma2.sequence = SEQ_UNCOMPRESSED_1;
1003
1004 if (tmp >= 0xC0) {
1005 /*
1006 * When there are new properties,
1007 * state reset is done at
1008 * SEQ_PROPERTIES.
1009 */
1010 s->lzma2.need_props = false;
1011 s->lzma2.next_sequence
1012 = SEQ_PROPERTIES;
1013
1014 } else if (s->lzma2.need_props) {
1015 return XZ_DATA_ERROR;
1016
1017 } else {
1018 s->lzma2.next_sequence
1019 = SEQ_LZMA_PREPARE;
1020 if (tmp >= 0xA0)
1021 lzma_reset(s);
1022 }
1023 } else {
1024 if (tmp > 0x02)
1025 return XZ_DATA_ERROR;
1026
1027 s->lzma2.sequence = SEQ_COMPRESSED_0;
1028 s->lzma2.next_sequence = SEQ_COPY;
1029 }
1030
1031 break;
1032
1033 case SEQ_UNCOMPRESSED_1:
1034 s->lzma2.uncompressed
1035 += (uint32_t)b->in[b->in_pos++] << 8;
1036 s->lzma2.sequence = SEQ_UNCOMPRESSED_2;
1037 break;
1038
1039 case SEQ_UNCOMPRESSED_2:
1040 s->lzma2.uncompressed
1041 += (uint32_t)b->in[b->in_pos++] + 1;
1042 s->lzma2.sequence = SEQ_COMPRESSED_0;
1043 break;
1044
1045 case SEQ_COMPRESSED_0:
1046 s->lzma2.compressed
1047 = (uint32_t)b->in[b->in_pos++] << 8;
1048 s->lzma2.sequence = SEQ_COMPRESSED_1;
1049 break;
1050
1051 case SEQ_COMPRESSED_1:
1052 s->lzma2.compressed
1053 += (uint32_t)b->in[b->in_pos++] + 1;
1054 s->lzma2.sequence = s->lzma2.next_sequence;
1055 break;
1056
1057 case SEQ_PROPERTIES:
1058 if (!lzma_props(s, b->in[b->in_pos++]))
1059 return XZ_DATA_ERROR;
1060
1061 s->lzma2.sequence = SEQ_LZMA_PREPARE;
1062
1063 /* Fall through */
1064
1065 case SEQ_LZMA_PREPARE:
1066 if (s->lzma2.compressed < RC_INIT_BYTES)
1067 return XZ_DATA_ERROR;
1068
1069 if (!rc_read_init(&s->rc, b))
1070 return XZ_OK;
1071
1072 s->lzma2.compressed -= RC_INIT_BYTES;
1073 s->lzma2.sequence = SEQ_LZMA_RUN;
1074
1075 /* Fall through */
1076
1077 case SEQ_LZMA_RUN:
1078 /*
1079 * Set dictionary limit to indicate how much we want
1080 * to be encoded at maximum. Decode new data into the
1081 * dictionary. Flush the new data from dictionary to
1082 * b->out. Check if we finished decoding this chunk.
1083 * In case the dictionary got full but we didn't fill
1084 * the output buffer yet, we may run this loop
1085 * multiple times without changing s->lzma2.sequence.
1086 */
1087 dict_limit(&s->dict, min_t(size_t,
1088 b->out_size - b->out_pos,
1089 s->lzma2.uncompressed));
1090 if (!lzma2_lzma(s, b))
1091 return XZ_DATA_ERROR;
1092
1093 s->lzma2.uncompressed -= dict_flush(&s->dict, b);
1094
1095 if (s->lzma2.uncompressed == 0) {
1096 if (s->lzma2.compressed > 0 || s->lzma.len > 0
1097 || !rc_is_finished(&s->rc))
1098 return XZ_DATA_ERROR;
1099
1100 rc_reset(&s->rc);
1101 s->lzma2.sequence = SEQ_CONTROL;
1102
1103 } else if (b->out_pos == b->out_size
1104 || (b->in_pos == b->in_size
1105 && s->temp.size
1106 < s->lzma2.compressed)) {
1107 return XZ_OK;
1108 }
1109
1110 break;
1111
1112 case SEQ_COPY:
1113 dict_uncompressed(&s->dict, b, &s->lzma2.compressed);
1114 if (s->lzma2.compressed > 0)
1115 return XZ_OK;
1116
1117 s->lzma2.sequence = SEQ_CONTROL;
1118 break;
1119 }
1120 }
1121
1122 return XZ_OK;
1123 }
1124
xz_dec_lzma2_create(enum xz_mode mode,uint32_t dict_max)1125 XZ_EXTERN struct xz_dec_lzma2 *xz_dec_lzma2_create(enum xz_mode mode,
1126 uint32_t dict_max)
1127 {
1128 struct xz_dec_lzma2 *s = kmalloc(sizeof(*s), GFP_KERNEL);
1129 if (s == NULL)
1130 return NULL;
1131
1132 s->dict.mode = mode;
1133 s->dict.size_max = dict_max;
1134
1135 if (DEC_IS_PREALLOC(mode)) {
1136 s->dict.buf = vmalloc(dict_max);
1137 if (s->dict.buf == NULL) {
1138 kfree(s);
1139 return NULL;
1140 }
1141 } else if (DEC_IS_DYNALLOC(mode)) {
1142 s->dict.buf = NULL;
1143 s->dict.allocated = 0;
1144 }
1145
1146 return s;
1147 }
1148
xz_dec_lzma2_reset(struct xz_dec_lzma2 * s,uint8_t props)1149 XZ_EXTERN enum xz_ret xz_dec_lzma2_reset(struct xz_dec_lzma2 *s, uint8_t props)
1150 {
1151 /* This limits dictionary size to 3 GiB to keep parsing simpler. */
1152 if (props > 39)
1153 return XZ_OPTIONS_ERROR;
1154
1155 s->dict.size = 2 + (props & 1);
1156 s->dict.size <<= (props >> 1) + 11;
1157
1158 if (DEC_IS_MULTI(s->dict.mode)) {
1159 if (s->dict.size > s->dict.size_max)
1160 return XZ_MEMLIMIT_ERROR;
1161
1162 s->dict.end = s->dict.size;
1163
1164 if (DEC_IS_DYNALLOC(s->dict.mode)) {
1165 if (s->dict.allocated < s->dict.size) {
1166 vfree(s->dict.buf);
1167 s->dict.buf = vmalloc(s->dict.size);
1168 if (s->dict.buf == NULL) {
1169 s->dict.allocated = 0;
1170 return XZ_MEM_ERROR;
1171 }
1172 }
1173 }
1174 }
1175
1176 s->lzma.len = 0;
1177
1178 s->lzma2.sequence = SEQ_CONTROL;
1179 s->lzma2.need_dict_reset = true;
1180
1181 s->temp.size = 0;
1182
1183 return XZ_OK;
1184 }
1185
xz_dec_lzma2_end(struct xz_dec_lzma2 * s)1186 XZ_EXTERN void xz_dec_lzma2_end(struct xz_dec_lzma2 *s)
1187 {
1188 if (DEC_IS_MULTI(s->dict.mode))
1189 vfree(s->dict.buf);
1190
1191 kfree(s);
1192 }
1193