1 /* 2 * XZ decompressor 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 #ifndef XZ_H 12 #define XZ_H 13 14 #ifdef __KERNEL__ 15 # include <linux/stddef.h> 16 # include <linux/types.h> 17 #else 18 # include <stddef.h> 19 # include <stdint.h> 20 #endif 21 22 /* In Linux, this is used to make extern functions static when needed. */ 23 #ifndef XZ_EXTERN 24 # define XZ_EXTERN extern 25 #endif 26 27 /** 28 * enum xz_mode - Operation mode 29 * 30 * @XZ_SINGLE: Single-call mode. This uses less RAM than 31 * multi-call modes, because the LZMA2 32 * dictionary doesn't need to be allocated as 33 * part of the decoder state. All required data 34 * structures are allocated at initialization, 35 * so xz_dec_run() cannot return XZ_MEM_ERROR. 36 * @XZ_PREALLOC: Multi-call mode with preallocated LZMA2 37 * dictionary buffer. All data structures are 38 * allocated at initialization, so xz_dec_run() 39 * cannot return XZ_MEM_ERROR. 40 * @XZ_DYNALLOC: Multi-call mode. The LZMA2 dictionary is 41 * allocated once the required size has been 42 * parsed from the stream headers. If the 43 * allocation fails, xz_dec_run() will return 44 * XZ_MEM_ERROR. 45 * 46 * It is possible to enable support only for a subset of the above 47 * modes at compile time by defining XZ_DEC_SINGLE, XZ_DEC_PREALLOC, 48 * or XZ_DEC_DYNALLOC. The xz_dec kernel module is always compiled 49 * with support for all operation modes, but the preboot code may 50 * be built with fewer features to minimize code size. 51 */ 52 enum xz_mode { 53 XZ_SINGLE, 54 XZ_PREALLOC, 55 XZ_DYNALLOC 56 }; 57 58 /** 59 * enum xz_ret - Return codes 60 * @XZ_OK: Everything is OK so far. More input or more 61 * output space is required to continue. This 62 * return code is possible only in multi-call mode 63 * (XZ_PREALLOC or XZ_DYNALLOC). 64 * @XZ_STREAM_END: Operation finished successfully. 65 * @XZ_UNSUPPORTED_CHECK: Integrity check type is not supported. Decoding 66 * is still possible in multi-call mode by simply 67 * calling xz_dec_run() again. 68 * Note that this return value is used only if 69 * XZ_DEC_ANY_CHECK was defined at build time, 70 * which is not used in the kernel. Unsupported 71 * check types return XZ_OPTIONS_ERROR if 72 * XZ_DEC_ANY_CHECK was not defined at build time. 73 * @XZ_MEM_ERROR: Allocating memory failed. This return code is 74 * possible only if the decoder was initialized 75 * with XZ_DYNALLOC. The amount of memory that was 76 * tried to be allocated was no more than the 77 * dict_max argument given to xz_dec_init(). 78 * @XZ_MEMLIMIT_ERROR: A bigger LZMA2 dictionary would be needed than 79 * allowed by the dict_max argument given to 80 * xz_dec_init(). This return value is possible 81 * only in multi-call mode (XZ_PREALLOC or 82 * XZ_DYNALLOC); the single-call mode (XZ_SINGLE) 83 * ignores the dict_max argument. 84 * @XZ_FORMAT_ERROR: File format was not recognized (wrong magic 85 * bytes). 86 * @XZ_OPTIONS_ERROR: This implementation doesn't support the requested 87 * compression options. In the decoder this means 88 * that the header CRC32 matches, but the header 89 * itself specifies something that we don't support. 90 * @XZ_DATA_ERROR: Compressed data is corrupt. 91 * @XZ_BUF_ERROR: Cannot make any progress. Details are slightly 92 * different between multi-call and single-call 93 * mode; more information below. 94 * 95 * In multi-call mode, XZ_BUF_ERROR is returned when two consecutive calls 96 * to XZ code cannot consume any input and cannot produce any new output. 97 * This happens when there is no new input available, or the output buffer 98 * is full while at least one output byte is still pending. Assuming your 99 * code is not buggy, you can get this error only when decoding a compressed 100 * stream that is truncated or otherwise corrupt. 101 * 102 * In single-call mode, XZ_BUF_ERROR is returned only when the output buffer 103 * is too small or the compressed input is corrupt in a way that makes the 104 * decoder produce more output than the caller expected. When it is 105 * (relatively) clear that the compressed input is truncated, XZ_DATA_ERROR 106 * is used instead of XZ_BUF_ERROR. 107 */ 108 enum xz_ret { 109 XZ_OK, 110 XZ_STREAM_END, 111 XZ_UNSUPPORTED_CHECK, 112 XZ_MEM_ERROR, 113 XZ_MEMLIMIT_ERROR, 114 XZ_FORMAT_ERROR, 115 XZ_OPTIONS_ERROR, 116 XZ_DATA_ERROR, 117 XZ_BUF_ERROR 118 }; 119 120 /** 121 * struct xz_buf - Passing input and output buffers to XZ code 122 * @in: Beginning of the input buffer. This may be NULL if and only 123 * if in_pos is equal to in_size. 124 * @in_pos: Current position in the input buffer. This must not exceed 125 * in_size. 126 * @in_size: Size of the input buffer 127 * @out: Beginning of the output buffer. This may be NULL if and only 128 * if out_pos is equal to out_size. 129 * @out_pos: Current position in the output buffer. This must not exceed 130 * out_size. 131 * @out_size: Size of the output buffer 132 * 133 * Only the contents of the output buffer from out[out_pos] onward, and 134 * the variables in_pos and out_pos are modified by the XZ code. 135 */ 136 struct xz_buf { 137 const uint8_t *in; 138 size_t in_pos; 139 size_t in_size; 140 141 uint8_t *out; 142 size_t out_pos; 143 size_t out_size; 144 }; 145 146 /** 147 * struct xz_dec - Opaque type to hold the XZ decoder state 148 */ 149 struct xz_dec; 150 151 /** 152 * xz_dec_init() - Allocate and initialize a XZ decoder state 153 * @mode: Operation mode 154 * @dict_max: Maximum size of the LZMA2 dictionary (history buffer) for 155 * multi-call decoding. This is ignored in single-call mode 156 * (mode == XZ_SINGLE). LZMA2 dictionary is always 2^n bytes 157 * or 2^n + 2^(n-1) bytes (the latter sizes are less common 158 * in practice), so other values for dict_max don't make sense. 159 * In the kernel, dictionary sizes of 64 KiB, 128 KiB, 256 KiB, 160 * 512 KiB, and 1 MiB are probably the only reasonable values, 161 * except for kernel and initramfs images where a bigger 162 * dictionary can be fine and useful. 163 * 164 * Single-call mode (XZ_SINGLE): xz_dec_run() decodes the whole stream at 165 * once. The caller must provide enough output space or the decoding will 166 * fail. The output space is used as the dictionary buffer, which is why 167 * there is no need to allocate the dictionary as part of the decoder's 168 * internal state. 169 * 170 * Because the output buffer is used as the workspace, streams encoded using 171 * a big dictionary are not a problem in single-call mode. It is enough that 172 * the output buffer is big enough to hold the actual uncompressed data; it 173 * can be smaller than the dictionary size stored in the stream headers. 174 * 175 * Multi-call mode with preallocated dictionary (XZ_PREALLOC): dict_max bytes 176 * of memory is preallocated for the LZMA2 dictionary. This way there is no 177 * risk that xz_dec_run() could run out of memory, since xz_dec_run() will 178 * never allocate any memory. Instead, if the preallocated dictionary is too 179 * small for decoding the given input stream, xz_dec_run() will return 180 * XZ_MEMLIMIT_ERROR. Thus, it is important to know what kind of data will be 181 * decoded to avoid allocating excessive amount of memory for the dictionary. 182 * 183 * Multi-call mode with dynamically allocated dictionary (XZ_DYNALLOC): 184 * dict_max specifies the maximum allowed dictionary size that xz_dec_run() 185 * may allocate once it has parsed the dictionary size from the stream 186 * headers. This way excessive allocations can be avoided while still 187 * limiting the maximum memory usage to a sane value to prevent running the 188 * system out of memory when decompressing streams from untrusted sources. 189 * 190 * On success, xz_dec_init() returns a pointer to struct xz_dec, which is 191 * ready to be used with xz_dec_run(). If memory allocation fails, 192 * xz_dec_init() returns NULL. 193 */ 194 XZ_EXTERN struct xz_dec *xz_dec_init(enum xz_mode mode, uint32_t dict_max); 195 196 /** 197 * xz_dec_run() - Run the XZ decoder 198 * @s: Decoder state allocated using xz_dec_init() 199 * @b: Input and output buffers 200 * 201 * The possible return values depend on build options and operation mode. 202 * See enum xz_ret for details. 203 * 204 * Note that if an error occurs in single-call mode (return value is not 205 * XZ_STREAM_END), b->in_pos and b->out_pos are not modified and the 206 * contents of the output buffer from b->out[b->out_pos] onward are 207 * undefined. This is true even after XZ_BUF_ERROR, because with some filter 208 * chains, there may be a second pass over the output buffer, and this pass 209 * cannot be properly done if the output buffer is truncated. Thus, you 210 * cannot give the single-call decoder a too small buffer and then expect to 211 * get that amount valid data from the beginning of the stream. You must use 212 * the multi-call decoder if you don't want to uncompress the whole stream. 213 */ 214 XZ_EXTERN enum xz_ret xz_dec_run(struct xz_dec *s, struct xz_buf *b); 215 216 /** 217 * xz_dec_reset() - Reset an already allocated decoder state 218 * @s: Decoder state allocated using xz_dec_init() 219 * 220 * This function can be used to reset the multi-call decoder state without 221 * freeing and reallocating memory with xz_dec_end() and xz_dec_init(). 222 * 223 * In single-call mode, xz_dec_reset() is always called in the beginning of 224 * xz_dec_run(). Thus, explicit call to xz_dec_reset() is useful only in 225 * multi-call mode. 226 */ 227 XZ_EXTERN void xz_dec_reset(struct xz_dec *s); 228 229 /** 230 * xz_dec_end() - Free the memory allocated for the decoder state 231 * @s: Decoder state allocated using xz_dec_init(). If s is NULL, 232 * this function does nothing. 233 */ 234 XZ_EXTERN void xz_dec_end(struct xz_dec *s); 235 236 /* 237 * Standalone build (userspace build or in-kernel build for boot time use) 238 * needs a CRC32 implementation. For normal in-kernel use, kernel's own 239 * CRC32 module is used instead, and users of this module don't need to 240 * care about the functions below. 241 */ 242 #ifndef XZ_INTERNAL_CRC32 243 # ifdef __KERNEL__ 244 # define XZ_INTERNAL_CRC32 0 245 # else 246 # define XZ_INTERNAL_CRC32 1 247 # endif 248 #endif 249 250 #if XZ_INTERNAL_CRC32 251 /* 252 * This must be called before any other xz_* function to initialize 253 * the CRC32 lookup table. 254 */ 255 XZ_EXTERN void xz_crc32_init(void); 256 257 /* 258 * Update CRC32 value using the polynomial from IEEE-802.3. To start a new 259 * calculation, the third argument must be zero. To continue the calculation, 260 * the previously returned value is passed as the third argument. 261 */ 262 XZ_EXTERN uint32_t xz_crc32(const uint8_t *buf, size_t size, uint32_t crc); 263 #endif 264 #endif 265