1 | /*
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2 | * XZ decompressor
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3 | *
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4 | * Authors: Lasse Collin <lasse.collin@tukaani.org>
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5 | * Igor Pavlov <http://7-zip.org/>
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6 | *
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7 | * This file has been put into the public domain.
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8 | * You can do whatever you want with this file.
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9 | */
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10 |
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11 | #ifndef XZ_H
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12 | #define XZ_H
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13 |
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14 | #ifdef __KERNEL__
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15 | # include <linux/stddef.h>
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16 | # include <linux/types.h>
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17 | #else
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18 | # include <stddef.h>
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19 | # include <stdint.h>
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20 | #endif
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21 |
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22 | /* In Linux, this is used to make extern functions static when needed. */
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23 | #ifndef XZ_EXTERN
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24 | # define XZ_EXTERN extern
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25 | #endif
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26 |
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27 | /* In Linux, this is used to mark the functions with __init when needed. */
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28 | #ifndef XZ_FUNC
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29 | # define XZ_FUNC
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30 | #endif
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31 |
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32 | /**
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33 | * enum xz_mode - Operation mode
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34 | *
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35 | * @XZ_SINGLE: Single-call mode. This uses less RAM than
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36 | * than multi-call modes, because the LZMA2
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37 | * dictionary doesn't need to be allocated as
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38 | * part of the decoder state. All required data
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39 | * structures are allocated at initialization,
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40 | * so xz_dec_run() cannot return XZ_MEM_ERROR.
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41 | * @XZ_PREALLOC: Multi-call mode with preallocated LZMA2
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42 | * dictionary buffer. All data structures are
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43 | * allocated at initialization, so xz_dec_run()
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44 | * cannot return XZ_MEM_ERROR.
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45 | * @XZ_DYNALLOC: Multi-call mode. The LZMA2 dictionary is
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46 | * allocated once the required size has been
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47 | * parsed from the stream headers. If the
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48 | * allocation fails, xz_dec_run() will return
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49 | * XZ_MEM_ERROR.
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50 | *
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51 | * It is possible to enable support only for a subset of the above
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52 | * modes at compile time by defining XZ_DEC_SINGLE, XZ_DEC_PREALLOC,
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53 | * or XZ_DEC_DYNALLOC. The xz_dec kernel module is always compiled
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54 | * with support for all operation modes, but the preboot code may
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55 | * be built with fewer features to minimize code size.
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56 | */
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57 | enum xz_mode {
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58 | XZ_SINGLE,
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59 | XZ_PREALLOC,
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60 | XZ_DYNALLOC
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61 | };
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62 |
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63 | /**
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64 | * enum xz_ret - Return codes
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65 | * @XZ_OK: Everything is OK so far. More input or more
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66 | * output space is required to continue. This
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67 | * return code is possible only in multi-call mode
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68 | * (XZ_PREALLOC or XZ_DYNALLOC).
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69 | * @XZ_STREAM_END: Operation finished successfully.
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70 | * @XZ_UNSUPPORTED_CHECK: Integrity check type is not supported. Decoding
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71 | * is still possible in multi-call mode by simply
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72 | * calling xz_dec_run() again.
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73 | * NOTE: This return value is used only if
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74 | * XZ_DEC_ANY_CHECK was defined at build time,
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75 | * which is not used in the kernel. Unsupported
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76 | * check types return XZ_OPTIONS_ERROR if
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77 | * XZ_DEC_ANY_CHECK was not defined at build time.
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78 | * @XZ_MEM_ERROR: Allocating memory failed. This return code is
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79 | * possible only if the decoder was initialized
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80 | * with XZ_DYNALLOC. The amount of memory that was
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81 | * tried to be allocated was no more than the
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82 | * dict_max argument given to xz_dec_init().
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83 | * @XZ_MEMLIMIT_ERROR: A bigger LZMA2 dictionary would be needed than
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84 | * allowed by the dict_max argument given to
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85 | * xz_dec_init(). This return value is possible
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86 | * only in multi-call mode (XZ_PREALLOC or
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87 | * XZ_DYNALLOC); the single-call mode (XZ_SINGLE)
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88 | * ignores the dict_max argument.
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89 | * @XZ_FORMAT_ERROR: File format was not recognized (wrong magic
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90 | * bytes).
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91 | * @XZ_OPTIONS_ERROR: This implementation doesn't support the requested
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92 | * compression options. In the decoder this means
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93 | * that the header CRC32 matches, but the header
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94 | * itself specifies something that we don't support.
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95 | * @XZ_DATA_ERROR: Compressed data is corrupt.
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96 | * @XZ_BUF_ERROR: Cannot make any progress. Details are slightly
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97 | * different between multi-call and single-call
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98 | * mode; more information below.
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99 | *
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100 | * In multi-call mode, XZ_BUF_ERROR is returned when two consecutive calls
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101 | * to XZ code cannot consume any input and cannot produce any new output.
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102 | * This happens when there is no new input available, or the output buffer
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103 | * is full while at least one output byte is still pending. Assuming your
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104 | * code is not buggy, you can get this error only when decoding a compressed
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105 | * stream that is truncated or otherwise corrupt.
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106 | *
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107 | * In single-call mode, XZ_BUF_ERROR is returned only when the output buffer
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108 | * is too small, or the compressed input is corrupt in a way that makes the
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109 | * decoder produce more output than the caller expected. When it is
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110 | * (relatively) clear that the compressed input is truncated, XZ_DATA_ERROR
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111 | * is used instead of XZ_BUF_ERROR.
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112 | */
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113 | enum xz_ret {
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114 | XZ_OK,
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115 | XZ_STREAM_END,
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116 | XZ_UNSUPPORTED_CHECK,
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117 | XZ_MEM_ERROR,
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118 | XZ_MEMLIMIT_ERROR,
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119 | XZ_FORMAT_ERROR,
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120 | XZ_OPTIONS_ERROR,
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121 | XZ_DATA_ERROR,
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122 | XZ_BUF_ERROR
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123 | };
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124 |
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125 | /**
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126 | * struct xz_buf - Passing input and output buffers to XZ code
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127 | * @in: Beginning of the input buffer. This may be NULL if and only
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128 | * if in_pos is equal to in_size.
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129 | * @in_pos: Current position in the input buffer. This must not exceed
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130 | * in_size.
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131 | * @in_size: Size of the input buffer
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132 | * @out: Beginning of the output buffer. This may be NULL if and only
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133 | * if out_pos is equal to out_size.
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134 | * @out_pos: Current position in the output buffer. This must not exceed
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135 | * out_size.
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136 | * @out_size: Size of the output buffer
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137 | *
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138 | * Only the contents of the output buffer from out[out_pos] onward, and
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139 | * the variables in_pos and out_pos are modified by the XZ code.
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140 | */
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141 | struct xz_buf {
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142 | const uint8_t *in;
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143 | size_t in_pos;
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144 | size_t in_size;
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145 |
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146 | uint8_t *out;
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147 | size_t out_pos;
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148 | size_t out_size;
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149 | };
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150 |
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151 | /**
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152 | * struct xz_dec - Opaque type to hold the XZ decoder state
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153 | */
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154 | struct xz_dec;
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155 |
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156 | /**
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157 | * xz_dec_init() - Allocate and initialize a XZ decoder state
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158 | * @mode: Operation mode
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159 | * @dict_max: Maximum size of the LZMA2 dictionary (history buffer) for
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160 | * multi-call decoding. This is ignored in single-call mode
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161 | * (mode == XZ_SINGLE). LZMA2 dictionary is always 2^n bytes
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162 | * or 2^n + 2^(n-1) bytes (the latter sizes are less common
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163 | * in practice), so other values for dict_max don't make sense.
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164 | * In the kernel, dictionary sizes of 64 KiB, 128 KiB, 256 KiB,
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165 | * 512 KiB, and 1 MiB are probably the only reasonable values,
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166 | * except for kernel and initramfs images where a bigger
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167 | * dictionary can be fine and useful.
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168 | *
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169 | * Single-call mode (XZ_SINGLE): xz_dec_run() decodes the whole stream at
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170 | * once. The caller must provide enough output space or the decoding will
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171 | * fail. The output space is used as the dictionary buffer, which is why
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172 | * there is no need to allocate the dictionary as part of the decoder's
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173 | * internal state.
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174 | *
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175 | * Because the output buffer is used as the workspace, streams encoded using
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176 | * a big dictionary are not a problem in single-call mode. It is enough that
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177 | * the output buffer is big enough to hold the actual uncompressed data; it
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178 | * can be smaller than the dictionary size stored in the stream headers.
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179 | *
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180 | * Multi-call mode with preallocated dictionary (XZ_PREALLOC): dict_max bytes
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181 | * of memory is preallocated for the LZMA2 dictionary. This way there is no
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182 | * risk that xz_dec_run() could run out of memory, since xz_dec_run() will
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183 | * never allocate any memory. Instead, if the preallocated dictionary is too
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184 | * small for decoding the given input stream, xz_dec_run() will return
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185 | * XZ_MEMLIMIT_ERROR. Thus, it is important to know what kind of data will be
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186 | * decoded to avoid allocating excessive amount of memory for the dictionary.
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187 | *
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188 | * Multi-call mode with dynamically allocated dictionary (XZ_DYNALLOC):
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189 | * dict_max specifies the maximum allowed dictionary size that xz_dec_run()
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190 | * may allocate once it has parsed the dictionary size from the stream
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191 | * headers. This way excessive allocations can be avoided while still
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192 | * limiting the maximum memory usage to a sane value to prevent running the
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193 | * system out of memory when decompressing streams from untrusted sources.
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194 | *
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195 | * On success, xz_dec_init() returns a pointer to struct xz_dec, which is
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196 | * ready to be used with xz_dec_run(). If memory allocation fails,
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197 | * xz_dec_init() returns NULL.
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198 | */
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199 | XZ_EXTERN struct xz_dec * XZ_FUNC xz_dec_init(
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200 | enum xz_mode mode, uint32_t dict_max);
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201 |
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202 | /**
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203 | * xz_dec_run() - Run the XZ decoder
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204 | * @s: Decoder state allocated using xz_dec_init()
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205 | * @b: Input and output buffers
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206 | *
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207 | * The possible return values depend on build options and operation mode.
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208 | * See enum xz_ret for details.
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209 | *
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210 | * NOTE: If an error occurs in single-call mode (return value is not
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211 | * XZ_STREAM_END), b->in_pos and b->out_pos are not modified, and the
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212 | * contents of the output buffer from b->out[b->out_pos] onward are
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213 | * undefined. This is true even after XZ_BUF_ERROR, because with some filter
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214 | * chains, there may be a second pass over the output buffer, and this pass
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215 | * cannot be properly done if the output buffer is truncated. Thus, you
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216 | * cannot give the single-call decoder a too small buffer and then expect to
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217 | * get that amount valid data from the beginning of the stream. You must use
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218 | * the multi-call decoder if you don't want to uncompress the whole stream.
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219 | */
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220 | XZ_EXTERN enum xz_ret XZ_FUNC xz_dec_run(struct xz_dec *s, struct xz_buf *b);
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221 |
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222 | /**
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223 | * xz_dec_reset() - Reset an already allocated decoder state
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224 | * @s: Decoder state allocated using xz_dec_init()
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225 | *
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226 | * This function can be used to reset the multi-call decoder state without
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227 | * freeing and reallocating memory with xz_dec_end() and xz_dec_init().
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228 | *
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229 | * In single-call mode, xz_dec_reset() is always called in the beginning of
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230 | * xz_dec_run(). Thus, explicit call to xz_dec_reset() is useful only in
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231 | * multi-call mode.
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232 | */
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233 | XZ_EXTERN void XZ_FUNC xz_dec_reset(struct xz_dec *s);
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234 |
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235 | /**
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236 | * xz_dec_end() - Free the memory allocated for the decoder state
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237 | * @s: Decoder state allocated using xz_dec_init(). If s is NULL,
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238 | * this function does nothing.
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239 | */
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240 | XZ_EXTERN void XZ_FUNC xz_dec_end(struct xz_dec *s);
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241 |
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242 | /*
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243 | * Standalone build (userspace build or in-kernel build for boot time use)
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244 | * needs a CRC32 implementation. For normal in-kernel use, kernel's own
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245 | * CRC32 module is used instead, and users of this module don't need to
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246 | * care about the functions below.
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247 | */
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248 | #ifndef XZ_INTERNAL_CRC32
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249 | # ifdef __KERNEL__
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250 | # define XZ_INTERNAL_CRC32 0
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251 | # else
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252 | # define XZ_INTERNAL_CRC32 1
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253 | # endif
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254 | #endif
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255 |
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256 | #if XZ_INTERNAL_CRC32
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257 | /*
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258 | * This must be called before any other xz_* function to initialize
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259 | * the CRC32 lookup table.
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260 | */
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261 | XZ_EXTERN void XZ_FUNC xz_crc32_init(void);
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262 |
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263 | /*
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264 | * Update CRC32 value using the polynomial from IEEE-802.3. To start a new
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265 | * calculation, the third argument must be zero. To continue the calculation,
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266 | * the previously returned value is passed as the third argument.
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267 | */
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268 | XZ_EXTERN uint32_t XZ_FUNC xz_crc32(
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269 | const uint8_t *buf, size_t size, uint32_t crc);
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270 | #endif
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271 | #endif
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