include/linux/xz.h

   1 /*
   2  * XZ decompressor
   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 #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  *                          than 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