1 /* SPDX-License-Identifier: 0BSD */ 2 3 /* 4 * XZ decompressor 5 * 6 * Authors: Lasse Collin <[email protected]> 7 * Igor Pavlov <https://7-zip.org/> 8 */ 9 10 #ifndef XZ_H 11 #define XZ_H 12 13 #ifdef __KERNEL__ 14 # include <linux/stddef.h> 15 # include <linux/types.h> 16 #else 17 # include <stddef.h> 18 # include <stdint.h> 19 #endif 20 21 #ifdef __cplusplus 22 extern "C" { 23 #endif 24 25 /* In Linux, this is used to make extern functions static when needed. */ 26 #ifndef XZ_EXTERN 27 # define XZ_EXTERN extern 28 #endif 29 30 /** 31 * enum xz_mode - Operation mode 32 * 33 * @XZ_SINGLE: Single-call mode. This uses less RAM than 34 * multi-call modes, because the LZMA2 35 * dictionary doesn't need to be allocated as 36 * part of the decoder state. All required data 37 * structures are allocated at initialization, 38 * so xz_dec_run() cannot return XZ_MEM_ERROR. 39 * @XZ_PREALLOC: Multi-call mode with preallocated LZMA2 40 * dictionary buffer. All data structures are 41 * allocated at initialization, so xz_dec_run() 42 * cannot return XZ_MEM_ERROR. 43 * @XZ_DYNALLOC: Multi-call mode. The LZMA2 dictionary is 44 * allocated once the required size has been 45 * parsed from the stream headers. If the 46 * allocation fails, xz_dec_run() will return 47 * XZ_MEM_ERROR. 48 * 49 * It is possible to enable support only for a subset of the above 50 * modes at compile time by defining XZ_DEC_SINGLE, XZ_DEC_PREALLOC, 51 * or XZ_DEC_DYNALLOC. The xz_dec kernel module is always compiled 52 * with support for all operation modes, but the preboot code may 53 * be built with fewer features to minimize code size. 54 */ 55 enum xz_mode { 56 XZ_SINGLE, 57 XZ_PREALLOC, 58 XZ_DYNALLOC 59 }; 60 61 /** 62 * enum xz_ret - Return codes 63 * @XZ_OK: Everything is OK so far. More input or more 64 * output space is required to continue. This 65 * return code is possible only in multi-call mode 66 * (XZ_PREALLOC or XZ_DYNALLOC). 67 * @XZ_STREAM_END: Operation finished successfully. 68 * @XZ_UNSUPPORTED_CHECK: Integrity check type is not supported. Decoding 69 * is still possible in multi-call mode by simply 70 * calling xz_dec_run() again. 71 * Note that this return value is used only if 72 * XZ_DEC_ANY_CHECK was defined at build time, 73 * which is not used in the kernel. Unsupported 74 * check types return XZ_OPTIONS_ERROR if 75 * XZ_DEC_ANY_CHECK was not defined at build time. 76 * @XZ_MEM_ERROR: Allocating memory failed. This return code is 77 * possible only if the decoder was initialized 78 * with XZ_DYNALLOC. The amount of memory that was 79 * tried to be allocated was no more than the 80 * dict_max argument given to xz_dec_init(). 81 * @XZ_MEMLIMIT_ERROR: A bigger LZMA2 dictionary would be needed than 82 * allowed by the dict_max argument given to 83 * xz_dec_init(). This return value is possible 84 * only in multi-call mode (XZ_PREALLOC or 85 * XZ_DYNALLOC); the single-call mode (XZ_SINGLE) 86 * ignores the dict_max argument. 87 * @XZ_FORMAT_ERROR: File format was not recognized (wrong magic 88 * bytes). 89 * @XZ_OPTIONS_ERROR: This implementation doesn't support the requested 90 * compression options. In the decoder this means 91 * that the header CRC32 matches, but the header 92 * itself specifies something that we don't support. 93 * @XZ_DATA_ERROR: Compressed data is corrupt. 94 * @XZ_BUF_ERROR: Cannot make any progress. Details are slightly 95 * different between multi-call and single-call 96 * mode; more information below. 97 * 98 * In multi-call mode, XZ_BUF_ERROR is returned when two consecutive calls 99 * to XZ code cannot consume any input and cannot produce any new output. 100 * This happens when there is no new input available, or the output buffer 101 * is full while at least one output byte is still pending. Assuming your 102 * code is not buggy, you can get this error only when decoding a compressed 103 * stream that is truncated or otherwise corrupt. 104 * 105 * In single-call mode, XZ_BUF_ERROR is returned only when the output buffer 106 * is too small or the compressed input is corrupt in a way that makes the 107 * decoder produce more output than the caller expected. When it is 108 * (relatively) clear that the compressed input is truncated, XZ_DATA_ERROR 109 * is used instead of XZ_BUF_ERROR. 110 */ 111 enum xz_ret { 112 XZ_OK, 113 XZ_STREAM_END, 114 XZ_UNSUPPORTED_CHECK, 115 XZ_MEM_ERROR, 116 XZ_MEMLIMIT_ERROR, 117 XZ_FORMAT_ERROR, 118 XZ_OPTIONS_ERROR, 119 XZ_DATA_ERROR, 120 XZ_BUF_ERROR 121 }; 122 123 /** 124 * struct xz_buf - Passing input and output buffers to XZ code 125 * @in: Beginning of the input buffer. This may be NULL if and only 126 * if in_pos is equal to in_size. 127 * @in_pos: Current position in the input buffer. This must not exceed 128 * in_size. 129 * @in_size: Size of the input buffer 130 * @out: Beginning of the output buffer. This may be NULL if and only 131 * if out_pos is equal to out_size. 132 * @out_pos: Current position in the output buffer. This must not exceed 133 * out_size. 134 * @out_size: Size of the output buffer 135 * 136 * Only the contents of the output buffer from out[out_pos] onward, and 137 * the variables in_pos and out_pos are modified by the XZ code. 138 */ 139 struct xz_buf { 140 const uint8_t *in; 141 size_t in_pos; 142 size_t in_size; 143 144 uint8_t *out; 145 size_t out_pos; 146 size_t out_size; 147 }; 148 149 /** 150 * struct xz_dec - Opaque type to hold the XZ decoder state 151 */ 152 struct xz_dec; 153 154 /** 155 * xz_dec_init() - Allocate and initialize a XZ decoder state 156 * @mode: Operation mode 157 * @dict_max: Maximum size of the LZMA2 dictionary (history buffer) for 158 * multi-call decoding. This is ignored in single-call mode 159 * (mode == XZ_SINGLE). LZMA2 dictionary is always 2^n bytes 160 * or 2^n + 2^(n-1) bytes (the latter sizes are less common 161 * in practice), so other values for dict_max don't make sense. 162 * In the kernel, dictionary sizes of 64 KiB, 128 KiB, 256 KiB, 163 * 512 KiB, and 1 MiB are probably the only reasonable values, 164 * except for kernel and initramfs images where a bigger 165 * dictionary can be fine and useful. 166 * 167 * Single-call mode (XZ_SINGLE): xz_dec_run() decodes the whole stream at 168 * once. The caller must provide enough output space or the decoding will 169 * fail. The output space is used as the dictionary buffer, which is why 170 * there is no need to allocate the dictionary as part of the decoder's 171 * internal state. 172 * 173 * Because the output buffer is used as the workspace, streams encoded using 174 * a big dictionary are not a problem in single-call mode. It is enough that 175 * the output buffer is big enough to hold the actual uncompressed data; it 176 * can be smaller than the dictionary size stored in the stream headers. 177 * 178 * Multi-call mode with preallocated dictionary (XZ_PREALLOC): dict_max bytes 179 * of memory is preallocated for the LZMA2 dictionary. This way there is no 180 * risk that xz_dec_run() could run out of memory, since xz_dec_run() will 181 * never allocate any memory. Instead, if the preallocated dictionary is too 182 * small for decoding the given input stream, xz_dec_run() will return 183 * XZ_MEMLIMIT_ERROR. Thus, it is important to know what kind of data will be 184 * decoded to avoid allocating excessive amount of memory for the dictionary. 185 * 186 * Multi-call mode with dynamically allocated dictionary (XZ_DYNALLOC): 187 * dict_max specifies the maximum allowed dictionary size that xz_dec_run() 188 * may allocate once it has parsed the dictionary size from the stream 189 * headers. This way excessive allocations can be avoided while still 190 * limiting the maximum memory usage to a sane value to prevent running the 191 * system out of memory when decompressing streams from untrusted sources. 192 * 193 * On success, xz_dec_init() returns a pointer to struct xz_dec, which is 194 * ready to be used with xz_dec_run(). If memory allocation fails, 195 * xz_dec_init() returns NULL. 196 */ 197 XZ_EXTERN struct xz_dec *xz_dec_init(enum xz_mode mode, uint32_t dict_max); 198 199 /** 200 * xz_dec_run() - Run the XZ decoder for a single XZ stream 201 * @s: Decoder state allocated using xz_dec_init() 202 * @b: Input and output buffers 203 * 204 * The possible return values depend on build options and operation mode. 205 * See enum xz_ret for details. 206 * 207 * Note that if an error occurs in single-call mode (return value is not 208 * XZ_STREAM_END), b->in_pos and b->out_pos are not modified and the 209 * contents of the output buffer from b->out[b->out_pos] onward are 210 * undefined. This is true even after XZ_BUF_ERROR, because with some filter 211 * chains, there may be a second pass over the output buffer, and this pass 212 * cannot be properly done if the output buffer is truncated. Thus, you 213 * cannot give the single-call decoder a too small buffer and then expect to 214 * get that amount valid data from the beginning of the stream. You must use 215 * the multi-call decoder if you don't want to uncompress the whole stream. 216 * 217 * Use xz_dec_run() when XZ data is stored inside some other file format. 218 * The decoding will stop after one XZ stream has been decompressed. To 219 * decompress regular .xz files which might have multiple concatenated 220 * streams, use xz_dec_catrun() instead. 221 */ 222 XZ_EXTERN enum xz_ret xz_dec_run(struct xz_dec *s, struct xz_buf *b); 223 224 /** 225 * xz_dec_catrun() - Run the XZ decoder with support for concatenated streams 226 * @s: Decoder state allocated using xz_dec_init() 227 * @b: Input and output buffers 228 * @finish: This is an int instead of bool to avoid requiring stdbool.h. 229 * As long as more input might be coming, finish must be false. 230 * When the caller knows that it has provided all the input to 231 * the decoder (some possibly still in b->in), it must set finish 232 * to true. Only when finish is true can this function return 233 * XZ_STREAM_END to indicate successful decompression of the 234 * file. In single-call mode (XZ_SINGLE) finish is assumed to 235 * always be true; the caller-provided value is ignored. 236 * 237 * This is like xz_dec_run() except that this makes it easy to decode .xz 238 * files with multiple streams (multiple .xz files concatenated as is). 239 * The rarely-used Stream Padding feature is supported too, that is, there 240 * can be null bytes after or between the streams. The number of null bytes 241 * must be a multiple of four. 242 * 243 * When finish is false and b->in_pos == b->in_size, it is possible that 244 * XZ_BUF_ERROR isn't returned even when no progress is possible (XZ_OK is 245 * returned instead). This shouldn't matter because in this situation a 246 * reasonable caller will attempt to provide more input or set finish to 247 * true for the next xz_dec_catrun() call anyway. 248 * 249 * For any struct xz_dec that has been initialized for multi-call mode: 250 * Once decoding has been started with xz_dec_run() or xz_dec_catrun(), 251 * the same function must be used until xz_dec_reset() or xz_dec_end(). 252 * Switching between the two decoding functions without resetting results 253 * in undefined behavior. 254 * 255 * xz_dec_catrun() is only available if XZ_DEC_CONCATENATED was defined 256 * at compile time. 257 */ 258 XZ_EXTERN enum xz_ret xz_dec_catrun(struct xz_dec *s, struct xz_buf *b, 259 int finish); 260 261 /** 262 * xz_dec_reset() - Reset an already allocated decoder state 263 * @s: Decoder state allocated using xz_dec_init() 264 * 265 * This function can be used to reset the multi-call decoder state without 266 * freeing and reallocating memory with xz_dec_end() and xz_dec_init(). 267 * 268 * In single-call mode, xz_dec_reset() is always called in the beginning of 269 * xz_dec_run(). Thus, explicit call to xz_dec_reset() is useful only in 270 * multi-call mode. 271 */ 272 XZ_EXTERN void xz_dec_reset(struct xz_dec *s); 273 274 /** 275 * xz_dec_end() - Free the memory allocated for the decoder state 276 * @s: Decoder state allocated using xz_dec_init(). If s is NULL, 277 * this function does nothing. 278 */ 279 XZ_EXTERN void xz_dec_end(struct xz_dec *s); 280 281 /* 282 * Decompressor for MicroLZMA, an LZMA variant with a very minimal header. 283 * See xz_dec_microlzma_alloc() below for details. 284 * 285 * These functions aren't used or available in preboot code and thus aren't 286 * marked with XZ_EXTERN. This avoids warnings about static functions that 287 * are never defined. 288 */ 289 /** 290 * struct xz_dec_microlzma - Opaque type to hold the MicroLZMA decoder state 291 */ 292 struct xz_dec_microlzma; 293 294 /** 295 * xz_dec_microlzma_alloc() - Allocate memory for the MicroLZMA decoder 296 * @mode XZ_SINGLE or XZ_PREALLOC 297 * @dict_size LZMA dictionary size. This must be at least 4 KiB and 298 * at most 3 GiB. 299 * 300 * In contrast to xz_dec_init(), this function only allocates the memory 301 * and remembers the dictionary size. xz_dec_microlzma_reset() must be used 302 * before calling xz_dec_microlzma_run(). 303 * 304 * The amount of allocated memory is a little less than 30 KiB with XZ_SINGLE. 305 * With XZ_PREALLOC also a dictionary buffer of dict_size bytes is allocated. 306 * 307 * On success, xz_dec_microlzma_alloc() returns a pointer to 308 * struct xz_dec_microlzma. If memory allocation fails or 309 * dict_size is invalid, NULL is returned. 310 * 311 * The compressed format supported by this decoder is a raw LZMA stream 312 * whose first byte (always 0x00) has been replaced with bitwise-negation 313 * of the LZMA properties (lc/lp/pb) byte. For example, if lc/lp/pb is 314 * 3/0/2, the first byte is 0xA2. This way the first byte can never be 0x00. 315 * Just like with LZMA2, lc + lp <= 4 must be true. The LZMA end-of-stream 316 * marker must not be used. The unused values are reserved for future use. 317 * This MicroLZMA header format was created for use in EROFS but may be used 318 * by others too. 319 */ 320 extern struct xz_dec_microlzma *xz_dec_microlzma_alloc(enum xz_mode mode, 321 uint32_t dict_size); 322 323 /** 324 * xz_dec_microlzma_reset() - Reset the MicroLZMA decoder state 325 * @s Decoder state allocated using xz_dec_microlzma_alloc() 326 * @comp_size Compressed size of the input stream 327 * @uncomp_size Uncompressed size of the input stream. A value smaller 328 * than the real uncompressed size of the input stream can 329 * be specified if uncomp_size_is_exact is set to false. 330 * uncomp_size can never be set to a value larger than the 331 * expected real uncompressed size because it would eventually 332 * result in XZ_DATA_ERROR. 333 * @uncomp_size_is_exact This is an int instead of bool to avoid 334 * requiring stdbool.h. This should normally be set to true. 335 * When this is set to false, error detection is weaker. 336 */ 337 extern void xz_dec_microlzma_reset(struct xz_dec_microlzma *s, 338 uint32_t comp_size, uint32_t uncomp_size, 339 int uncomp_size_is_exact); 340 341 /** 342 * xz_dec_microlzma_run() - Run the MicroLZMA decoder 343 * @s Decoder state initialized using xz_dec_microlzma_reset() 344 * @b: Input and output buffers 345 * 346 * This works similarly to xz_dec_run() with a few important differences. 347 * Only the differences are documented here. 348 * 349 * The only possible return values are XZ_OK, XZ_STREAM_END, and 350 * XZ_DATA_ERROR. This function cannot return XZ_BUF_ERROR: if no progress 351 * is possible due to lack of input data or output space, this function will 352 * keep returning XZ_OK. Thus, the calling code must be written so that it 353 * will eventually provide input and output space matching (or exceeding) 354 * comp_size and uncomp_size arguments given to xz_dec_microlzma_reset(). 355 * If the caller cannot do this (for example, if the input file is truncated 356 * or otherwise corrupt), the caller must detect this error by itself to 357 * avoid an infinite loop. 358 * 359 * If the compressed data seems to be corrupt, XZ_DATA_ERROR is returned. 360 * This can happen also when incorrect dictionary, uncompressed, or 361 * compressed sizes have been specified. 362 * 363 * With XZ_PREALLOC only: As an extra feature, b->out may be NULL to skip over 364 * uncompressed data. This way the caller doesn't need to provide a temporary 365 * output buffer for the bytes that will be ignored. 366 * 367 * With XZ_SINGLE only: In contrast to xz_dec_run(), the return value XZ_OK 368 * is also possible and thus XZ_SINGLE is actually a limited multi-call mode. 369 * After XZ_OK the bytes decoded so far may be read from the output buffer. 370 * It is possible to continue decoding but the variables b->out and b->out_pos 371 * MUST NOT be changed by the caller. Increasing the value of b->out_size is 372 * allowed to make more output space available; one doesn't need to provide 373 * space for the whole uncompressed data on the first call. The input buffer 374 * may be changed normally like with XZ_PREALLOC. This way input data can be 375 * provided from non-contiguous memory. 376 */ 377 extern enum xz_ret xz_dec_microlzma_run(struct xz_dec_microlzma *s, 378 struct xz_buf *b); 379 380 /** 381 * xz_dec_microlzma_end() - Free the memory allocated for the decoder state 382 * @s: Decoder state allocated using xz_dec_microlzma_alloc(). 383 * If s is NULL, this function does nothing. 384 */ 385 extern void xz_dec_microlzma_end(struct xz_dec_microlzma *s); 386 387 /* 388 * Standalone build (userspace build or in-kernel build for boot time use) 389 * needs a CRC32 implementation. For normal in-kernel use, kernel's own 390 * CRC32 module is used instead, and users of this module don't need to 391 * care about the functions below. 392 */ 393 #ifndef XZ_INTERNAL_CRC32 394 # ifdef __KERNEL__ 395 # define XZ_INTERNAL_CRC32 0 396 # else 397 # define XZ_INTERNAL_CRC32 1 398 # endif 399 #endif 400 401 /* 402 * If CRC64 support has been enabled with XZ_USE_CRC64, a CRC64 403 * implementation is needed too. 404 */ 405 #ifndef XZ_USE_CRC64 406 # undef XZ_INTERNAL_CRC64 407 # define XZ_INTERNAL_CRC64 0 408 #endif 409 #ifndef XZ_INTERNAL_CRC64 410 # ifdef __KERNEL__ 411 # error Using CRC64 in the kernel has not been implemented. 412 # else 413 # define XZ_INTERNAL_CRC64 1 414 # endif 415 #endif 416 417 #if XZ_INTERNAL_CRC32 418 /* 419 * This must be called before any other xz_* function to initialize 420 * the CRC32 lookup table. 421 */ 422 XZ_EXTERN void xz_crc32_init(void); 423 424 /* 425 * Update CRC32 value using the polynomial from IEEE-802.3. To start a new 426 * calculation, the third argument must be zero. To continue the calculation, 427 * the previously returned value is passed as the third argument. 428 */ 429 XZ_EXTERN uint32_t xz_crc32(const uint8_t *buf, size_t size, uint32_t crc); 430 #endif 431 432 #if XZ_INTERNAL_CRC64 433 /* 434 * This must be called before any other xz_* function (except xz_crc32_init()) 435 * to initialize the CRC64 lookup table. 436 */ 437 XZ_EXTERN void xz_crc64_init(void); 438 439 /* 440 * Update CRC64 value using the polynomial from ECMA-182. To start a new 441 * calculation, the third argument must be zero. To continue the calculation, 442 * the previously returned value is passed as the third argument. 443 */ 444 XZ_EXTERN uint64_t xz_crc64(const uint8_t *buf, size_t size, uint64_t crc); 445 #endif 446 447 #ifdef __cplusplus 448 } 449 #endif 450 451 #endif 452