/* SPDX-License-Identifier: 0BSD */ /* * XZ decompressor * * Authors: Lasse Collin <[email protected]> * Igor Pavlov <https://7-zip.org/> */ #ifndef XZ_H #define XZ_H #ifdef __KERNEL__ # include <linux/stddef.h> # include <linux/types.h> #else # include <stddef.h> # include <stdint.h> #endif /** * enum xz_mode - Operation mode * * @XZ_SINGLE: Single-call mode. This uses less RAM than * multi-call modes, because the LZMA2 * dictionary doesn't need to be allocated as * part of the decoder state. All required data * structures are allocated at initialization, * so xz_dec_run() cannot return XZ_MEM_ERROR. * @XZ_PREALLOC: Multi-call mode with preallocated LZMA2 * dictionary buffer. All data structures are * allocated at initialization, so xz_dec_run() * cannot return XZ_MEM_ERROR. * @XZ_DYNALLOC: Multi-call mode. The LZMA2 dictionary is * allocated once the required size has been * parsed from the stream headers. If the * allocation fails, xz_dec_run() will return * XZ_MEM_ERROR. * * It is possible to enable support only for a subset of the above * modes at compile time by defining XZ_DEC_SINGLE, XZ_DEC_PREALLOC, * or XZ_DEC_DYNALLOC. The xz_dec kernel module is always compiled * with support for all operation modes, but the preboot code may * be built with fewer features to minimize code size. */ enum xz_mode { … }; /** * enum xz_ret - Return codes * @XZ_OK: Everything is OK so far. More input or more * output space is required to continue. This * return code is possible only in multi-call mode * (XZ_PREALLOC or XZ_DYNALLOC). * @XZ_STREAM_END: Operation finished successfully. * @XZ_UNSUPPORTED_CHECK: Integrity check type is not supported. Decoding * is still possible in multi-call mode by simply * calling xz_dec_run() again. * Note that this return value is used only if * XZ_DEC_ANY_CHECK was defined at build time, * which is not used in the kernel. Unsupported * check types return XZ_OPTIONS_ERROR if * XZ_DEC_ANY_CHECK was not defined at build time. * @XZ_MEM_ERROR: Allocating memory failed. This return code is * possible only if the decoder was initialized * with XZ_DYNALLOC. The amount of memory that was * tried to be allocated was no more than the * dict_max argument given to xz_dec_init(). * @XZ_MEMLIMIT_ERROR: A bigger LZMA2 dictionary would be needed than * allowed by the dict_max argument given to * xz_dec_init(). This return value is possible * only in multi-call mode (XZ_PREALLOC or * XZ_DYNALLOC); the single-call mode (XZ_SINGLE) * ignores the dict_max argument. * @XZ_FORMAT_ERROR: File format was not recognized (wrong magic * bytes). * @XZ_OPTIONS_ERROR: This implementation doesn't support the requested * compression options. In the decoder this means * that the header CRC32 matches, but the header * itself specifies something that we don't support. * @XZ_DATA_ERROR: Compressed data is corrupt. * @XZ_BUF_ERROR: Cannot make any progress. Details are slightly * different between multi-call and single-call * mode; more information below. * * In multi-call mode, XZ_BUF_ERROR is returned when two consecutive calls * to XZ code cannot consume any input and cannot produce any new output. * This happens when there is no new input available, or the output buffer * is full while at least one output byte is still pending. Assuming your * code is not buggy, you can get this error only when decoding a compressed * stream that is truncated or otherwise corrupt. * * In single-call mode, XZ_BUF_ERROR is returned only when the output buffer * is too small or the compressed input is corrupt in a way that makes the * decoder produce more output than the caller expected. When it is * (relatively) clear that the compressed input is truncated, XZ_DATA_ERROR * is used instead of XZ_BUF_ERROR. */ enum xz_ret { … }; /** * struct xz_buf - Passing input and output buffers to XZ code * @in: Beginning of the input buffer. This may be NULL if and only * if in_pos is equal to in_size. * @in_pos: Current position in the input buffer. This must not exceed * in_size. * @in_size: Size of the input buffer * @out: Beginning of the output buffer. This may be NULL if and only * if out_pos is equal to out_size. * @out_pos: Current position in the output buffer. This must not exceed * out_size. * @out_size: Size of the output buffer * * Only the contents of the output buffer from out[out_pos] onward, and * the variables in_pos and out_pos are modified by the XZ code. */ struct xz_buf { … }; /* * struct xz_dec - Opaque type to hold the XZ decoder state */ struct xz_dec; /** * xz_dec_init() - Allocate and initialize a XZ decoder state * @mode: Operation mode * @dict_max: Maximum size of the LZMA2 dictionary (history buffer) for * multi-call decoding. This is ignored in single-call mode * (mode == XZ_SINGLE). LZMA2 dictionary is always 2^n bytes * or 2^n + 2^(n-1) bytes (the latter sizes are less common * in practice), so other values for dict_max don't make sense. * In the kernel, dictionary sizes of 64 KiB, 128 KiB, 256 KiB, * 512 KiB, and 1 MiB are probably the only reasonable values, * except for kernel and initramfs images where a bigger * dictionary can be fine and useful. * * Single-call mode (XZ_SINGLE): xz_dec_run() decodes the whole stream at * once. The caller must provide enough output space or the decoding will * fail. The output space is used as the dictionary buffer, which is why * there is no need to allocate the dictionary as part of the decoder's * internal state. * * Because the output buffer is used as the workspace, streams encoded using * a big dictionary are not a problem in single-call mode. It is enough that * the output buffer is big enough to hold the actual uncompressed data; it * can be smaller than the dictionary size stored in the stream headers. * * Multi-call mode with preallocated dictionary (XZ_PREALLOC): dict_max bytes * of memory is preallocated for the LZMA2 dictionary. This way there is no * risk that xz_dec_run() could run out of memory, since xz_dec_run() will * never allocate any memory. Instead, if the preallocated dictionary is too * small for decoding the given input stream, xz_dec_run() will return * XZ_MEMLIMIT_ERROR. Thus, it is important to know what kind of data will be * decoded to avoid allocating excessive amount of memory for the dictionary. * * Multi-call mode with dynamically allocated dictionary (XZ_DYNALLOC): * dict_max specifies the maximum allowed dictionary size that xz_dec_run() * may allocate once it has parsed the dictionary size from the stream * headers. This way excessive allocations can be avoided while still * limiting the maximum memory usage to a sane value to prevent running the * system out of memory when decompressing streams from untrusted sources. * * On success, xz_dec_init() returns a pointer to struct xz_dec, which is * ready to be used with xz_dec_run(). If memory allocation fails, * xz_dec_init() returns NULL. */ struct xz_dec *xz_dec_init(enum xz_mode mode, uint32_t dict_max); /** * xz_dec_run() - Run the XZ decoder * @s: Decoder state allocated using xz_dec_init() * @b: Input and output buffers * * The possible return values depend on build options and operation mode. * See enum xz_ret for details. * * Note that if an error occurs in single-call mode (return value is not * XZ_STREAM_END), b->in_pos and b->out_pos are not modified and the * contents of the output buffer from b->out[b->out_pos] onward are * undefined. This is true even after XZ_BUF_ERROR, because with some filter * chains, there may be a second pass over the output buffer, and this pass * cannot be properly done if the output buffer is truncated. Thus, you * cannot give the single-call decoder a too small buffer and then expect to * get that amount valid data from the beginning of the stream. You must use * the multi-call decoder if you don't want to uncompress the whole stream. */ enum xz_ret xz_dec_run(struct xz_dec *s, struct xz_buf *b); /** * xz_dec_reset() - Reset an already allocated decoder state * @s: Decoder state allocated using xz_dec_init() * * This function can be used to reset the multi-call decoder state without * freeing and reallocating memory with xz_dec_end() and xz_dec_init(). * * In single-call mode, xz_dec_reset() is always called in the beginning of * xz_dec_run(). Thus, explicit call to xz_dec_reset() is useful only in * multi-call mode. */ void xz_dec_reset(struct xz_dec *s); /** * xz_dec_end() - Free the memory allocated for the decoder state * @s: Decoder state allocated using xz_dec_init(). If s is NULL, * this function does nothing. */ void xz_dec_end(struct xz_dec *s); /** * DOC: MicroLZMA decompressor * * This MicroLZMA header format was created for use in EROFS but may be used * by others too. **In most cases one needs the XZ APIs above instead.** * * The compressed format supported by this decoder is a raw LZMA stream * whose first byte (always 0x00) has been replaced with bitwise-negation * of the LZMA properties (lc/lp/pb) byte. For example, if lc/lp/pb is * 3/0/2, the first byte is 0xA2. This way the first byte can never be 0x00. * Just like with LZMA2, lc + lp <= 4 must be true. The LZMA end-of-stream * marker must not be used. The unused values are reserved for future use. */ /* * struct xz_dec_microlzma - Opaque type to hold the MicroLZMA decoder state */ struct xz_dec_microlzma; /** * xz_dec_microlzma_alloc() - Allocate memory for the MicroLZMA decoder * @mode: XZ_SINGLE or XZ_PREALLOC * @dict_size: LZMA dictionary size. This must be at least 4 KiB and * at most 3 GiB. * * In contrast to xz_dec_init(), this function only allocates the memory * and remembers the dictionary size. xz_dec_microlzma_reset() must be used * before calling xz_dec_microlzma_run(). * * The amount of allocated memory is a little less than 30 KiB with XZ_SINGLE. * With XZ_PREALLOC also a dictionary buffer of dict_size bytes is allocated. * * On success, xz_dec_microlzma_alloc() returns a pointer to * struct xz_dec_microlzma. If memory allocation fails or * dict_size is invalid, NULL is returned. */ struct xz_dec_microlzma *xz_dec_microlzma_alloc(enum xz_mode mode, uint32_t dict_size); /** * xz_dec_microlzma_reset() - Reset the MicroLZMA decoder state * @s: Decoder state allocated using xz_dec_microlzma_alloc() * @comp_size: Compressed size of the input stream * @uncomp_size: Uncompressed size of the input stream. A value smaller * than the real uncompressed size of the input stream can * be specified if uncomp_size_is_exact is set to false. * uncomp_size can never be set to a value larger than the * expected real uncompressed size because it would eventually * result in XZ_DATA_ERROR. * @uncomp_size_is_exact: This is an int instead of bool to avoid * requiring stdbool.h. This should normally be set to true. * When this is set to false, error detection is weaker. */ void xz_dec_microlzma_reset(struct xz_dec_microlzma *s, uint32_t comp_size, uint32_t uncomp_size, int uncomp_size_is_exact); /** * xz_dec_microlzma_run() - Run the MicroLZMA decoder * @s: Decoder state initialized using xz_dec_microlzma_reset() * @b: Input and output buffers * * This works similarly to xz_dec_run() with a few important differences. * Only the differences are documented here. * * The only possible return values are XZ_OK, XZ_STREAM_END, and * XZ_DATA_ERROR. This function cannot return XZ_BUF_ERROR: if no progress * is possible due to lack of input data or output space, this function will * keep returning XZ_OK. Thus, the calling code must be written so that it * will eventually provide input and output space matching (or exceeding) * comp_size and uncomp_size arguments given to xz_dec_microlzma_reset(). * If the caller cannot do this (for example, if the input file is truncated * or otherwise corrupt), the caller must detect this error by itself to * avoid an infinite loop. * * If the compressed data seems to be corrupt, XZ_DATA_ERROR is returned. * This can happen also when incorrect dictionary, uncompressed, or * compressed sizes have been specified. * * With XZ_PREALLOC only: As an extra feature, b->out may be NULL to skip over * uncompressed data. This way the caller doesn't need to provide a temporary * output buffer for the bytes that will be ignored. * * With XZ_SINGLE only: In contrast to xz_dec_run(), the return value XZ_OK * is also possible and thus XZ_SINGLE is actually a limited multi-call mode. * After XZ_OK the bytes decoded so far may be read from the output buffer. * It is possible to continue decoding but the variables b->out and b->out_pos * MUST NOT be changed by the caller. Increasing the value of b->out_size is * allowed to make more output space available; one doesn't need to provide * space for the whole uncompressed data on the first call. The input buffer * may be changed normally like with XZ_PREALLOC. This way input data can be * provided from non-contiguous memory. */ enum xz_ret xz_dec_microlzma_run(struct xz_dec_microlzma *s, struct xz_buf *b); /** * xz_dec_microlzma_end() - Free the memory allocated for the decoder state * @s: Decoder state allocated using xz_dec_microlzma_alloc(). * If s is NULL, this function does nothing. */ void xz_dec_microlzma_end(struct xz_dec_microlzma *s); /* * Standalone build (userspace build or in-kernel build for boot time use) * needs a CRC32 implementation. For normal in-kernel use, kernel's own * CRC32 module is used instead, and users of this module don't need to * care about the functions below. */ #ifndef XZ_INTERNAL_CRC32 # ifdef __KERNEL__ #define XZ_INTERNAL_CRC32 … # else #define XZ_INTERNAL_CRC32 … # endif #endif #if XZ_INTERNAL_CRC32 /* * This must be called before any other xz_* function to initialize * the CRC32 lookup table. */ void xz_crc32_init(void); /* * Update CRC32 value using the polynomial from IEEE-802.3. To start a new * calculation, the third argument must be zero. To continue the calculation, * the previously returned value is passed as the third argument. */ uint32_t xz_crc32(const uint8_t *buf, size_t size, uint32_t crc); #endif #endif
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