1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * 4 * Copyright (C) 2019-2021 Paragon Software GmbH, All rights reserved. 5 * 6 */ 7 8 #include <linux/kernel.h> 9 #include <linux/slab.h> 10 #include <linux/stddef.h> 11 #include <linux/string.h> 12 #include <linux/types.h> 13 14 #include "debug.h" 15 #include "ntfs_fs.h" 16 17 // clang-format off 18 /* Src buffer is zero. */ 19 #define LZNT_ERROR_ALL_ZEROS 1 20 #define LZNT_CHUNK_SIZE 0x1000 21 // clang-format on 22 23 struct lznt_hash { 24 const u8 *p1; 25 const u8 *p2; 26 }; 27 28 struct lznt { 29 const u8 *unc; 30 const u8 *unc_end; 31 const u8 *best_match; 32 size_t max_len; 33 bool std; 34 35 struct lznt_hash hash[LZNT_CHUNK_SIZE]; 36 }; 37 38 static inline size_t get_match_len(const u8 *ptr, const u8 *end, const u8 *prev, 39 size_t max_len) 40 { 41 size_t len = 0; 42 43 while (ptr + len < end && ptr[len] == prev[len] && ++len < max_len) 44 ; 45 return len; 46 } 47 48 static size_t longest_match_std(const u8 *src, struct lznt *ctx) 49 { 50 size_t hash_index; 51 size_t len1 = 0, len2 = 0; 52 const u8 **hash; 53 54 hash_index = 55 ((40543U * ((((src[0] << 4) ^ src[1]) << 4) ^ src[2])) >> 4) & 56 (LZNT_CHUNK_SIZE - 1); 57 58 hash = &(ctx->hash[hash_index].p1); 59 60 if (hash[0] >= ctx->unc && hash[0] < src && hash[0][0] == src[0] && 61 hash[0][1] == src[1] && hash[0][2] == src[2]) { 62 len1 = 3; 63 if (ctx->max_len > 3) 64 len1 += get_match_len(src + 3, ctx->unc_end, 65 hash[0] + 3, ctx->max_len - 3); 66 } 67 68 if (hash[1] >= ctx->unc && hash[1] < src && hash[1][0] == src[0] && 69 hash[1][1] == src[1] && hash[1][2] == src[2]) { 70 len2 = 3; 71 if (ctx->max_len > 3) 72 len2 += get_match_len(src + 3, ctx->unc_end, 73 hash[1] + 3, ctx->max_len - 3); 74 } 75 76 /* Compare two matches and select the best one. */ 77 if (len1 < len2) { 78 ctx->best_match = hash[1]; 79 len1 = len2; 80 } else { 81 ctx->best_match = hash[0]; 82 } 83 84 hash[1] = hash[0]; 85 hash[0] = src; 86 return len1; 87 } 88 89 static size_t longest_match_best(const u8 *src, struct lznt *ctx) 90 { 91 size_t max_len; 92 const u8 *ptr; 93 94 if (ctx->unc >= src || !ctx->max_len) 95 return 0; 96 97 max_len = 0; 98 for (ptr = ctx->unc; ptr < src; ++ptr) { 99 size_t len = 100 get_match_len(src, ctx->unc_end, ptr, ctx->max_len); 101 if (len >= max_len) { 102 max_len = len; 103 ctx->best_match = ptr; 104 } 105 } 106 107 return max_len >= 3 ? max_len : 0; 108 } 109 110 static const size_t s_max_len[] = { 111 0x1002, 0x802, 0x402, 0x202, 0x102, 0x82, 0x42, 0x22, 0x12, 112 }; 113 114 static const size_t s_max_off[] = { 115 0x10, 0x20, 0x40, 0x80, 0x100, 0x200, 0x400, 0x800, 0x1000, 116 }; 117 118 static inline u16 make_pair(size_t offset, size_t len, size_t index) 119 { 120 return ((offset - 1) << (12 - index)) | 121 ((len - 3) & (((1 << (12 - index)) - 1))); 122 } 123 124 static inline size_t parse_pair(u16 pair, size_t *offset, size_t index) 125 { 126 *offset = 1 + (pair >> (12 - index)); 127 return 3 + (pair & ((1 << (12 - index)) - 1)); 128 } 129 130 /* 131 * compress_chunk 132 * 133 * Return: 134 * * 0 - Ok, @cmpr contains @cmpr_chunk_size bytes of compressed data. 135 * * 1 - Input buffer is full zero. 136 * * -2 - The compressed buffer is too small to hold the compressed data. 137 */ 138 static inline int compress_chunk(size_t (*match)(const u8 *, struct lznt *), 139 const u8 *unc, const u8 *unc_end, u8 *cmpr, 140 u8 *cmpr_end, size_t *cmpr_chunk_size, 141 struct lznt *ctx) 142 { 143 size_t cnt = 0; 144 size_t idx = 0; 145 const u8 *up = unc; 146 u8 *cp = cmpr + 3; 147 u8 *cp2 = cmpr + 2; 148 u8 not_zero = 0; 149 /* Control byte of 8-bit values: ( 0 - means byte as is, 1 - short pair ). */ 150 u8 ohdr = 0; 151 u8 *last; 152 u16 t16; 153 154 if (unc + LZNT_CHUNK_SIZE < unc_end) 155 unc_end = unc + LZNT_CHUNK_SIZE; 156 157 last = min(cmpr + LZNT_CHUNK_SIZE + sizeof(short), cmpr_end); 158 159 ctx->unc = unc; 160 ctx->unc_end = unc_end; 161 ctx->max_len = s_max_len[0]; 162 163 while (up < unc_end) { 164 size_t max_len; 165 166 while (unc + s_max_off[idx] < up) 167 ctx->max_len = s_max_len[++idx]; 168 169 /* Find match. */ 170 max_len = up + 3 <= unc_end ? (*match)(up, ctx) : 0; 171 172 if (!max_len) { 173 if (cp >= last) 174 goto NotCompressed; 175 not_zero |= *cp++ = *up++; 176 } else if (cp + 1 >= last) { 177 goto NotCompressed; 178 } else { 179 t16 = make_pair(up - ctx->best_match, max_len, idx); 180 *cp++ = t16; 181 *cp++ = t16 >> 8; 182 183 ohdr |= 1 << cnt; 184 up += max_len; 185 } 186 187 cnt = (cnt + 1) & 7; 188 if (!cnt) { 189 *cp2 = ohdr; 190 ohdr = 0; 191 cp2 = cp; 192 cp += 1; 193 } 194 } 195 196 if (cp2 < last) 197 *cp2 = ohdr; 198 else 199 cp -= 1; 200 201 *cmpr_chunk_size = cp - cmpr; 202 203 t16 = (*cmpr_chunk_size - 3) | 0xB000; 204 cmpr[0] = t16; 205 cmpr[1] = t16 >> 8; 206 207 return not_zero ? 0 : LZNT_ERROR_ALL_ZEROS; 208 209 NotCompressed: 210 211 if ((cmpr + LZNT_CHUNK_SIZE + sizeof(short)) > last) 212 return -2; 213 214 /* 215 * Copy non cmpr data. 216 * 0x3FFF == ((LZNT_CHUNK_SIZE + 2 - 3) | 0x3000) 217 */ 218 cmpr[0] = 0xff; 219 cmpr[1] = 0x3f; 220 221 memcpy(cmpr + sizeof(short), unc, LZNT_CHUNK_SIZE); 222 *cmpr_chunk_size = LZNT_CHUNK_SIZE + sizeof(short); 223 224 return 0; 225 } 226 227 static inline ssize_t decompress_chunk(u8 *unc, u8 *unc_end, const u8 *cmpr, 228 const u8 *cmpr_end) 229 { 230 u8 *up = unc; 231 u8 ch = *cmpr++; 232 size_t bit = 0; 233 size_t index = 0; 234 u16 pair; 235 size_t offset, length; 236 237 /* Do decompression until pointers are inside range. */ 238 while (up < unc_end && cmpr < cmpr_end) { 239 /* Correct index */ 240 while (unc + s_max_off[index] < up) 241 index += 1; 242 243 /* Check the current flag for zero. */ 244 if (!(ch & (1 << bit))) { 245 /* Just copy byte. */ 246 *up++ = *cmpr++; 247 goto next; 248 } 249 250 /* Check for boundary. */ 251 if (cmpr + 1 >= cmpr_end) 252 return -EINVAL; 253 254 /* Read a short from little endian stream. */ 255 pair = cmpr[1]; 256 pair <<= 8; 257 pair |= cmpr[0]; 258 259 cmpr += 2; 260 261 /* Translate packed information into offset and length. */ 262 length = parse_pair(pair, &offset, index); 263 264 /* Check offset for boundary. */ 265 if (unc + offset > up) 266 return -EINVAL; 267 268 /* Truncate the length if necessary. */ 269 if (up + length >= unc_end) 270 length = unc_end - up; 271 272 /* Now we copy bytes. This is the heart of LZ algorithm. */ 273 for (; length > 0; length--, up++) 274 *up = *(up - offset); 275 276 next: 277 /* Advance flag bit value. */ 278 bit = (bit + 1) & 7; 279 280 if (!bit) { 281 if (cmpr >= cmpr_end) 282 break; 283 284 ch = *cmpr++; 285 } 286 } 287 288 /* Return the size of uncompressed data. */ 289 return up - unc; 290 } 291 292 /* 293 * get_lznt_ctx 294 * @level: 0 - Standard compression. 295 * !0 - Best compression, requires a lot of cpu. 296 */ 297 struct lznt *get_lznt_ctx(int level) 298 { 299 struct lznt *r = kzalloc(level ? offsetof(struct lznt, hash) : 300 sizeof(struct lznt), 301 GFP_NOFS); 302 303 if (r) 304 r->std = !level; 305 return r; 306 } 307 308 /* 309 * compress_lznt - Compresses @unc into @cmpr 310 * 311 * Return: 312 * * +x - Ok, @cmpr contains 'final_compressed_size' bytes of compressed data. 313 * * 0 - Input buffer is full zero. 314 */ 315 size_t compress_lznt(const void *unc, size_t unc_size, void *cmpr, 316 size_t cmpr_size, struct lznt *ctx) 317 { 318 int err; 319 size_t (*match)(const u8 *src, struct lznt *ctx); 320 u8 *p = cmpr; 321 u8 *end = p + cmpr_size; 322 const u8 *unc_chunk = unc; 323 const u8 *unc_end = unc_chunk + unc_size; 324 bool is_zero = true; 325 326 if (ctx->std) { 327 match = &longest_match_std; 328 memset(ctx->hash, 0, sizeof(ctx->hash)); 329 } else { 330 match = &longest_match_best; 331 } 332 333 /* Compression cycle. */ 334 for (; unc_chunk < unc_end; unc_chunk += LZNT_CHUNK_SIZE) { 335 cmpr_size = 0; 336 err = compress_chunk(match, unc_chunk, unc_end, p, end, 337 &cmpr_size, ctx); 338 if (err < 0) 339 return unc_size; 340 341 if (is_zero && err != LZNT_ERROR_ALL_ZEROS) 342 is_zero = false; 343 344 p += cmpr_size; 345 } 346 347 if (p <= end - 2) 348 p[0] = p[1] = 0; 349 350 return is_zero ? 0 : PtrOffset(cmpr, p); 351 } 352 353 /* 354 * decompress_lznt - Decompress @cmpr into @unc. 355 */ 356 ssize_t decompress_lznt(const void *cmpr, size_t cmpr_size, void *unc, 357 size_t unc_size) 358 { 359 const u8 *cmpr_chunk = cmpr; 360 const u8 *cmpr_end = cmpr_chunk + cmpr_size; 361 u8 *unc_chunk = unc; 362 u8 *unc_end = unc_chunk + unc_size; 363 u16 chunk_hdr; 364 365 if (cmpr_size < sizeof(short)) 366 return -EINVAL; 367 368 /* Read chunk header. */ 369 chunk_hdr = cmpr_chunk[1]; 370 chunk_hdr <<= 8; 371 chunk_hdr |= cmpr_chunk[0]; 372 373 /* Loop through decompressing chunks. */ 374 for (;;) { 375 size_t chunk_size_saved; 376 size_t unc_use; 377 size_t cmpr_use = 3 + (chunk_hdr & (LZNT_CHUNK_SIZE - 1)); 378 379 /* Check that the chunk actually fits the supplied buffer. */ 380 if (cmpr_chunk + cmpr_use > cmpr_end) 381 return -EINVAL; 382 383 /* First make sure the chunk contains compressed data. */ 384 if (chunk_hdr & 0x8000) { 385 /* Decompress a chunk and return if we get an error. */ 386 ssize_t err = 387 decompress_chunk(unc_chunk, unc_end, 388 cmpr_chunk + sizeof(chunk_hdr), 389 cmpr_chunk + cmpr_use); 390 if (err < 0) 391 return err; 392 unc_use = err; 393 } else { 394 /* This chunk does not contain compressed data. */ 395 unc_use = unc_chunk + LZNT_CHUNK_SIZE > unc_end ? 396 unc_end - unc_chunk : 397 LZNT_CHUNK_SIZE; 398 399 if (cmpr_chunk + sizeof(chunk_hdr) + unc_use > 400 cmpr_end) { 401 return -EINVAL; 402 } 403 404 memcpy(unc_chunk, cmpr_chunk + sizeof(chunk_hdr), 405 unc_use); 406 } 407 408 /* Advance pointers. */ 409 cmpr_chunk += cmpr_use; 410 unc_chunk += unc_use; 411 412 /* Check for the end of unc buffer. */ 413 if (unc_chunk >= unc_end) 414 break; 415 416 /* Proceed the next chunk. */ 417 if (cmpr_chunk > cmpr_end - 2) 418 break; 419 420 chunk_size_saved = LZNT_CHUNK_SIZE; 421 422 /* Read chunk header. */ 423 chunk_hdr = cmpr_chunk[1]; 424 chunk_hdr <<= 8; 425 chunk_hdr |= cmpr_chunk[0]; 426 427 if (!chunk_hdr) 428 break; 429 430 /* Check the size of unc buffer. */ 431 if (unc_use < chunk_size_saved) { 432 size_t t1 = chunk_size_saved - unc_use; 433 u8 *t2 = unc_chunk + t1; 434 435 /* 'Zero' memory. */ 436 if (t2 >= unc_end) 437 break; 438 439 memset(unc_chunk, 0, t1); 440 unc_chunk = t2; 441 } 442 } 443 444 /* Check compression boundary. */ 445 if (cmpr_chunk > cmpr_end) 446 return -EINVAL; 447 448 /* 449 * The unc size is just a difference between current 450 * pointer and original one. 451 */ 452 return PtrOffset(unc, unc_chunk); 453 } 454