1 | /*
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2 | * Branch/Call/Jump (BCJ) filter decoders
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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 | #include "xz_private.h"
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12 |
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13 | /*
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14 | * The rest of the file is inside this ifdef. It makes things a little more
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15 | * convenient when building without support for any BCJ filters.
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16 | */
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17 | #ifdef XZ_DEC_BCJ
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18 |
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19 | struct xz_dec_bcj {
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20 | /* Type of the BCJ filter being used */
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21 | enum {
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22 | BCJ_X86 = 4, /* x86 or x86-64 */
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23 | BCJ_POWERPC = 5, /* Big endian only */
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24 | BCJ_IA64 = 6, /* Big or little endian */
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25 | BCJ_ARM = 7, /* Little endian only */
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26 | BCJ_ARMTHUMB = 8, /* Little endian only */
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27 | BCJ_SPARC = 9 /* Big or little endian */
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28 | } type;
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29 |
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30 | /*
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31 | * Return value of the next filter in the chain. We need to preserve
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32 | * this information across calls, because we must not call the next
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33 | * filter anymore once it has returned XZ_STREAM_END.
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34 | */
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35 | enum xz_ret ret;
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36 |
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37 | /* True if we are operating in single-call mode. */
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38 | bool single_call;
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39 |
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40 | /*
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41 | * Absolute position relative to the beginning of the uncompressed
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42 | * data (in a single .xz Block). We care only about the lowest 32
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43 | * bits so this doesn't need to be uint64_t even with big files.
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44 | */
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45 | uint32_t pos;
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46 |
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47 | /* x86 filter state */
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48 | uint32_t x86_prev_mask;
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49 |
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50 | /* Temporary space to hold the variables from struct xz_buf */
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51 | uint8_t *out;
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52 | size_t out_pos;
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53 | size_t out_size;
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54 |
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55 | struct {
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56 | /* Amount of already filtered data in the beginning of buf */
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57 | size_t filtered;
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58 |
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59 | /* Total amount of data currently stored in buf */
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60 | size_t size;
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61 |
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62 | /*
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63 | * Buffer to hold a mix of filtered and unfiltered data. This
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64 | * needs to be big enough to hold Alignment + 2 * Look-ahead:
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65 | *
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66 | * Type Alignment Look-ahead
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67 | * x86 1 4
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68 | * PowerPC 4 0
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69 | * IA-64 16 0
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70 | * ARM 4 0
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71 | * ARM-Thumb 2 2
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72 | * SPARC 4 0
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73 | */
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74 | uint8_t buf[16];
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75 | } temp;
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76 | };
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77 |
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78 | #ifdef XZ_DEC_X86
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79 | /*
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80 | * This is used to test the most significant byte of a memory address
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81 | * in an x86 instruction.
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82 | */
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83 | static inline int bcj_x86_test_msbyte(uint8_t b)
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84 | {
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85 | return b == 0x00 || b == 0xFF;
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86 | }
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87 |
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88 | static noinline_for_stack size_t XZ_FUNC bcj_x86(
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89 | struct xz_dec_bcj *s, uint8_t *buf, size_t size)
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90 | {
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91 | static const bool mask_to_allowed_status[8]
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92 | = { true, true, true, false, true, false, false, false };
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93 |
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94 | static const uint8_t mask_to_bit_num[8] = { 0, 1, 2, 2, 3, 3, 3, 3 };
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95 |
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96 | size_t i;
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97 | size_t prev_pos = (size_t)-1;
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98 | uint32_t prev_mask = s->x86_prev_mask;
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99 | uint32_t src;
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100 | uint32_t dest;
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101 | uint32_t j;
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102 | uint8_t b;
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103 |
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104 | if (size <= 4)
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105 | return 0;
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106 |
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107 | size -= 4;
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108 | for (i = 0; i < size; ++i) {
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109 | if ((buf[i] & 0xFE) != 0xE8)
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110 | continue;
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111 |
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112 | prev_pos = i - prev_pos;
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113 | if (prev_pos > 3) {
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114 | prev_mask = 0;
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115 | } else {
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116 | prev_mask = (prev_mask << (prev_pos - 1)) & 7;
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117 | if (prev_mask != 0) {
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118 | b = buf[i + 4 - mask_to_bit_num[prev_mask]];
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119 | if (!mask_to_allowed_status[prev_mask]
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120 | || bcj_x86_test_msbyte(b)) {
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121 | prev_pos = i;
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122 | prev_mask = (prev_mask << 1) | 1;
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123 | continue;
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124 | }
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125 | }
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126 | }
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127 |
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128 | prev_pos = i;
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129 |
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130 | if (bcj_x86_test_msbyte(buf[i + 4])) {
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131 | src = get_unaligned_le32(buf + i + 1);
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132 | while (true) {
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133 | dest = src - (s->pos + (uint32_t)i + 5);
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134 | if (prev_mask == 0)
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135 | break;
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136 |
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137 | j = mask_to_bit_num[prev_mask] * 8;
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138 | b = (uint8_t)(dest >> (24 - j));
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139 | if (!bcj_x86_test_msbyte(b))
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140 | break;
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141 |
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142 | src = dest ^ (((uint32_t)1 << (32 - j)) - 1);
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143 | }
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144 |
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145 | dest &= 0x01FFFFFF;
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146 | dest |= (uint32_t)0 - (dest & 0x01000000);
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147 | put_unaligned_le32(dest, buf + i + 1);
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148 | i += 4;
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149 | } else {
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150 | prev_mask = (prev_mask << 1) | 1;
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151 | }
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152 | }
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153 |
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154 | prev_pos = i - prev_pos;
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155 | s->x86_prev_mask = prev_pos > 3 ? 0 : prev_mask << (prev_pos - 1);
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156 | return i;
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157 | }
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158 | #endif
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159 |
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160 | #ifdef XZ_DEC_POWERPC
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161 | static noinline_for_stack size_t XZ_FUNC bcj_powerpc(
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162 | struct xz_dec_bcj *s, uint8_t *buf, size_t size)
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163 | {
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164 | size_t i;
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165 | uint32_t instr;
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166 |
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167 | for (i = 0; i + 4 <= size; i += 4) {
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168 | instr = get_unaligned_be32(buf + i);
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169 | if ((instr & 0xFC000003) == 0x48000001) {
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170 | instr &= 0x03FFFFFC;
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171 | instr -= s->pos + (uint32_t)i;
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172 | instr &= 0x03FFFFFC;
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173 | instr |= 0x48000001;
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174 | put_unaligned_be32(instr, buf + i);
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175 | }
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176 | }
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177 |
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178 | return i;
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179 | }
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180 | #endif
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181 |
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182 | #ifdef XZ_DEC_IA64
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183 | static noinline_for_stack size_t XZ_FUNC bcj_ia64(
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184 | struct xz_dec_bcj *s, uint8_t *buf, size_t size)
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185 | {
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186 | static const uint8_t branch_table[32] = {
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187 | 0, 0, 0, 0, 0, 0, 0, 0,
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188 | 0, 0, 0, 0, 0, 0, 0, 0,
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189 | 4, 4, 6, 6, 0, 0, 7, 7,
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190 | 4, 4, 0, 0, 4, 4, 0, 0
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191 | };
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192 |
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193 | /*
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194 | * The local variables take a little bit stack space, but it's less
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195 | * than what LZMA2 decoder takes, so it doesn't make sense to reduce
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196 | * stack usage here without doing that for the LZMA2 decoder too.
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197 | */
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198 |
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199 | /* Loop counters */
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200 | size_t i;
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201 | size_t j;
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202 |
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203 | /* Instruction slot (0, 1, or 2) in the 128-bit instruction word */
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204 | uint32_t slot;
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205 |
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206 | /* Bitwise offset of the instruction indicated by slot */
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207 | uint32_t bit_pos;
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208 |
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209 | /* bit_pos split into byte and bit parts */
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210 | uint32_t byte_pos;
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211 | uint32_t bit_res;
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212 |
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213 | /* Address part of an instruction */
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214 | uint32_t addr;
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215 |
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216 | /* Mask used to detect which instructions to convert */
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217 | uint32_t mask;
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218 |
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219 | /* 41-bit instruction stored somewhere in the lowest 48 bits */
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220 | uint64_t instr;
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221 |
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222 | /* Instruction normalized with bit_res for easier manipulation */
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223 | uint64_t norm;
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224 |
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225 | for (i = 0; i + 16 <= size; i += 16) {
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226 | mask = branch_table[buf[i] & 0x1F];
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227 | for (slot = 0, bit_pos = 5; slot < 3; ++slot, bit_pos += 41) {
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228 | if (((mask >> slot) & 1) == 0)
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229 | continue;
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230 |
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231 | byte_pos = bit_pos >> 3;
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232 | bit_res = bit_pos & 7;
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233 | instr = 0;
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234 | for (j = 0; j < 6; ++j)
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235 | instr |= (uint64_t)(buf[i + j + byte_pos])
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236 | << (8 * j);
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237 |
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238 | norm = instr >> bit_res;
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239 |
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240 | if (((norm >> 37) & 0x0F) == 0x05
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241 | && ((norm >> 9) & 0x07) == 0) {
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242 | addr = (norm >> 13) & 0x0FFFFF;
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243 | addr |= ((uint32_t)(norm >> 36) & 1) << 20;
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244 | addr <<= 4;
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245 | addr -= s->pos + (uint32_t)i;
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246 | addr >>= 4;
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247 |
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248 | norm &= ~((uint64_t)0x8FFFFF << 13);
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249 | norm |= (uint64_t)(addr & 0x0FFFFF) << 13;
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250 | norm |= (uint64_t)(addr & 0x100000)
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251 | << (36 - 20);
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252 |
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253 | instr &= (1 << bit_res) - 1;
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254 | instr |= norm << bit_res;
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255 |
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256 | for (j = 0; j < 6; j++)
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257 | buf[i + j + byte_pos]
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258 | = (uint8_t)(instr >> (8 * j));
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259 | }
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260 | }
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261 | }
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262 |
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263 | return i;
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264 | }
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265 | #endif
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266 |
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267 | #ifdef XZ_DEC_ARM
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268 | static noinline_for_stack size_t XZ_FUNC bcj_arm(
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269 | struct xz_dec_bcj *s, uint8_t *buf, size_t size)
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270 | {
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271 | size_t i;
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272 | uint32_t addr;
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273 |
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274 | for (i = 0; i + 4 <= size; i += 4) {
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275 | if (buf[i + 3] == 0xEB) {
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276 | addr = (uint32_t)buf[i] | ((uint32_t)buf[i + 1] << 8)
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277 | | ((uint32_t)buf[i + 2] << 16);
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278 | addr <<= 2;
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279 | addr -= s->pos + (uint32_t)i + 8;
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280 | addr >>= 2;
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281 | buf[i] = (uint8_t)addr;
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282 | buf[i + 1] = (uint8_t)(addr >> 8);
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283 | buf[i + 2] = (uint8_t)(addr >> 16);
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284 | }
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285 | }
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286 |
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287 | return i;
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288 | }
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289 | #endif
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290 |
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291 | #ifdef XZ_DEC_ARMTHUMB
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292 | static noinline_for_stack size_t XZ_FUNC bcj_armthumb(
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293 | struct xz_dec_bcj *s, uint8_t *buf, size_t size)
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294 | {
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295 | size_t i;
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296 | uint32_t addr;
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297 |
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298 | for (i = 0; i + 4 <= size; i += 2) {
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299 | if ((buf[i + 1] & 0xF8) == 0xF0
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300 | && (buf[i + 3] & 0xF8) == 0xF8) {
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301 | addr = (((uint32_t)buf[i + 1] & 0x07) << 19)
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302 | | ((uint32_t)buf[i] << 11)
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303 | | (((uint32_t)buf[i + 3] & 0x07) << 8)
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304 | | (uint32_t)buf[i + 2];
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305 | addr <<= 1;
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306 | addr -= s->pos + (uint32_t)i + 4;
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307 | addr >>= 1;
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308 | buf[i + 1] = (uint8_t)(0xF0 | ((addr >> 19) & 0x07));
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309 | buf[i] = (uint8_t)(addr >> 11);
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310 | buf[i + 3] = (uint8_t)(0xF8 | ((addr >> 8) & 0x07));
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311 | buf[i + 2] = (uint8_t)addr;
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312 | i += 2;
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313 | }
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314 | }
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315 |
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316 | return i;
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317 | }
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318 | #endif
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319 |
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320 | #ifdef XZ_DEC_SPARC
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321 | static noinline_for_stack size_t XZ_FUNC bcj_sparc(
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322 | struct xz_dec_bcj *s, uint8_t *buf, size_t size)
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323 | {
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324 | size_t i;
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325 | uint32_t instr;
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326 |
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327 | for (i = 0; i + 4 <= size; i += 4) {
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328 | instr = get_unaligned_be32(buf + i);
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329 | if ((instr >> 22) == 0x100 || (instr >> 22) == 0x1FF) {
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330 | instr <<= 2;
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331 | instr -= s->pos + (uint32_t)i;
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332 | instr >>= 2;
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333 | instr = ((uint32_t)0x40000000 - (instr & 0x400000))
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334 | | 0x40000000 | (instr & 0x3FFFFF);
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335 | put_unaligned_be32(instr, buf + i);
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336 | }
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337 | }
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338 |
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339 | return i;
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340 | }
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341 | #endif
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342 |
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343 | /*
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344 | * Apply the selected BCJ filter. Update *pos and s->pos to match the amount
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345 | * of data that got filtered.
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346 | *
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347 | * NOTE: This is implemented as a switch statement to avoid using function
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348 | * pointers, which could be problematic in the kernel boot code, which must
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349 | * avoid pointers to static data (at least on x86).
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350 | */
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351 | static void XZ_FUNC bcj_apply(struct xz_dec_bcj *s,
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352 | uint8_t *buf, size_t *pos, size_t size)
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353 | {
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354 | size_t filtered;
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355 |
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356 | buf += *pos;
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357 | size -= *pos;
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358 |
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359 | switch (s->type) {
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360 | #ifdef XZ_DEC_X86
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361 | case BCJ_X86:
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362 | filtered = bcj_x86(s, buf, size);
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363 | break;
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364 | #endif
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365 | #ifdef XZ_DEC_POWERPC
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366 | case BCJ_POWERPC:
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367 | filtered = bcj_powerpc(s, buf, size);
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368 | break;
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369 | #endif
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370 | #ifdef XZ_DEC_IA64
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371 | case BCJ_IA64:
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372 | filtered = bcj_ia64(s, buf, size);
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373 | break;
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374 | #endif
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375 | #ifdef XZ_DEC_ARM
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376 | case BCJ_ARM:
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377 | filtered = bcj_arm(s, buf, size);
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378 | break;
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379 | #endif
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380 | #ifdef XZ_DEC_ARMTHUMB
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381 | case BCJ_ARMTHUMB:
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382 | filtered = bcj_armthumb(s, buf, size);
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383 | break;
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384 | #endif
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385 | #ifdef XZ_DEC_SPARC
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386 | case BCJ_SPARC:
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387 | filtered = bcj_sparc(s, buf, size);
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388 | break;
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389 | #endif
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390 | default:
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391 | /* Never reached but silence compiler warnings. */
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392 | filtered = 0;
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393 | break;
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394 | }
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395 |
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396 | *pos += filtered;
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397 | s->pos += filtered;
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398 | }
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399 |
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400 | /*
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401 | * Flush pending filtered data from temp to the output buffer.
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402 | * Move the remaining mixture of possibly filtered and unfiltered
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403 | * data to the beginning of temp.
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404 | */
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405 | static void XZ_FUNC bcj_flush(struct xz_dec_bcj *s, struct xz_buf *b)
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406 | {
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407 | size_t copy_size;
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408 |
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409 | copy_size = min_t(size_t, s->temp.filtered, b->out_size - b->out_pos);
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410 | memcpy(b->out + b->out_pos, s->temp.buf, copy_size);
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411 | b->out_pos += copy_size;
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412 |
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413 | s->temp.filtered -= copy_size;
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414 | s->temp.size -= copy_size;
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415 | memmove(s->temp.buf, s->temp.buf + copy_size, s->temp.size);
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416 | }
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417 |
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418 | /*
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419 | * The BCJ filter functions are primitive in sense that they process the
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420 | * data in chunks of 1-16 bytes. To hide this issue, this function does
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421 | * some buffering.
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422 | */
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423 | XZ_EXTERN enum xz_ret XZ_FUNC xz_dec_bcj_run(struct xz_dec_bcj *s,
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424 | struct xz_dec_lzma2 *lzma2, struct xz_buf *b)
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425 | {
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426 | size_t out_start;
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427 |
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428 | /*
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429 | * Flush pending already filtered data to the output buffer. Return
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430 | * immediatelly if we couldn't flush everything, or if the next
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431 | * filter in the chain had already returned XZ_STREAM_END.
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432 | */
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433 | if (s->temp.filtered > 0) {
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434 | bcj_flush(s, b);
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435 | if (s->temp.filtered > 0)
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436 | return XZ_OK;
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437 |
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438 | if (s->ret == XZ_STREAM_END)
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439 | return XZ_STREAM_END;
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440 | }
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441 |
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442 | /*
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443 | * If we have more output space than what is currently pending in
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444 | * temp, copy the unfiltered data from temp to the output buffer
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445 | * and try to fill the output buffer by decoding more data from the
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446 | * next filter in the chain. Apply the BCJ filter on the new data
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447 | * in the output buffer. If everything cannot be filtered, copy it
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448 | * to temp and rewind the output buffer position accordingly.
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449 | *
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450 | * This needs to be always run when temp.size == 0 to handle a special
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451 | * case where the output buffer is full and the next filter has no
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452 | * more output coming but hasn't returned XZ_STREAM_END yet.
|
---|
453 | */
|
---|
454 | if (s->temp.size < b->out_size - b->out_pos || s->temp.size == 0) {
|
---|
455 | out_start = b->out_pos;
|
---|
456 | memcpy(b->out + b->out_pos, s->temp.buf, s->temp.size);
|
---|
457 | b->out_pos += s->temp.size;
|
---|
458 |
|
---|
459 | s->ret = xz_dec_lzma2_run(lzma2, b);
|
---|
460 | if (s->ret != XZ_STREAM_END
|
---|
461 | && (s->ret != XZ_OK || s->single_call))
|
---|
462 | return s->ret;
|
---|
463 |
|
---|
464 | bcj_apply(s, b->out, &out_start, b->out_pos);
|
---|
465 |
|
---|
466 | /*
|
---|
467 | * As an exception, if the next filter returned XZ_STREAM_END,
|
---|
468 | * we can do that too, since the last few bytes that remain
|
---|
469 | * unfiltered are meant to remain unfiltered.
|
---|
470 | */
|
---|
471 | if (s->ret == XZ_STREAM_END)
|
---|
472 | return XZ_STREAM_END;
|
---|
473 |
|
---|
474 | s->temp.size = b->out_pos - out_start;
|
---|
475 | b->out_pos -= s->temp.size;
|
---|
476 | memcpy(s->temp.buf, b->out + b->out_pos, s->temp.size);
|
---|
477 |
|
---|
478 | /*
|
---|
479 | * If there wasn't enough input to the next filter to fill
|
---|
480 | * the output buffer with unfiltered data, there's no point
|
---|
481 | * to try decoding more data to temp.
|
---|
482 | */
|
---|
483 | if (b->out_pos + s->temp.size < b->out_size)
|
---|
484 | return XZ_OK;
|
---|
485 | }
|
---|
486 |
|
---|
487 | /*
|
---|
488 | * We have unfiltered data in temp. If the output buffer isn't full
|
---|
489 | * yet, try to fill the temp buffer by decoding more data from the
|
---|
490 | * next filter. Apply the BCJ filter on temp. Then we hopefully can
|
---|
491 | * fill the actual output buffer by copying filtered data from temp.
|
---|
492 | * A mix of filtered and unfiltered data may be left in temp; it will
|
---|
493 | * be taken care on the next call to this function.
|
---|
494 | */
|
---|
495 | if (b->out_pos < b->out_size) {
|
---|
496 | /* Make b->out{,_pos,_size} temporarily point to s->temp. */
|
---|
497 | s->out = b->out;
|
---|
498 | s->out_pos = b->out_pos;
|
---|
499 | s->out_size = b->out_size;
|
---|
500 | b->out = s->temp.buf;
|
---|
501 | b->out_pos = s->temp.size;
|
---|
502 | b->out_size = sizeof(s->temp.buf);
|
---|
503 |
|
---|
504 | s->ret = xz_dec_lzma2_run(lzma2, b);
|
---|
505 |
|
---|
506 | s->temp.size = b->out_pos;
|
---|
507 | b->out = s->out;
|
---|
508 | b->out_pos = s->out_pos;
|
---|
509 | b->out_size = s->out_size;
|
---|
510 |
|
---|
511 | if (s->ret != XZ_OK && s->ret != XZ_STREAM_END)
|
---|
512 | return s->ret;
|
---|
513 |
|
---|
514 | bcj_apply(s, s->temp.buf, &s->temp.filtered, s->temp.size);
|
---|
515 |
|
---|
516 | /*
|
---|
517 | * If the next filter returned XZ_STREAM_END, we mark that
|
---|
518 | * everything is filtered, since the last unfiltered bytes
|
---|
519 | * of the stream are meant to be left as is.
|
---|
520 | */
|
---|
521 | if (s->ret == XZ_STREAM_END)
|
---|
522 | s->temp.filtered = s->temp.size;
|
---|
523 |
|
---|
524 | bcj_flush(s, b);
|
---|
525 | if (s->temp.filtered > 0)
|
---|
526 | return XZ_OK;
|
---|
527 | }
|
---|
528 |
|
---|
529 | return s->ret;
|
---|
530 | }
|
---|
531 |
|
---|
532 | XZ_EXTERN struct xz_dec_bcj * XZ_FUNC xz_dec_bcj_create(bool single_call)
|
---|
533 | {
|
---|
534 | struct xz_dec_bcj *s = kmalloc(sizeof(*s), GFP_KERNEL);
|
---|
535 | if (s != NULL)
|
---|
536 | s->single_call = single_call;
|
---|
537 |
|
---|
538 | return s;
|
---|
539 | }
|
---|
540 |
|
---|
541 | XZ_EXTERN enum xz_ret XZ_FUNC xz_dec_bcj_reset(
|
---|
542 | struct xz_dec_bcj *s, uint8_t id)
|
---|
543 | {
|
---|
544 | switch (id) {
|
---|
545 | #ifdef XZ_DEC_X86
|
---|
546 | case BCJ_X86:
|
---|
547 | #endif
|
---|
548 | #ifdef XZ_DEC_POWERPC
|
---|
549 | case BCJ_POWERPC:
|
---|
550 | #endif
|
---|
551 | #ifdef XZ_DEC_IA64
|
---|
552 | case BCJ_IA64:
|
---|
553 | #endif
|
---|
554 | #ifdef XZ_DEC_ARM
|
---|
555 | case BCJ_ARM:
|
---|
556 | #endif
|
---|
557 | #ifdef XZ_DEC_ARMTHUMB
|
---|
558 | case BCJ_ARMTHUMB:
|
---|
559 | #endif
|
---|
560 | #ifdef XZ_DEC_SPARC
|
---|
561 | case BCJ_SPARC:
|
---|
562 | #endif
|
---|
563 | break;
|
---|
564 |
|
---|
565 | default:
|
---|
566 | /* Unsupported Filter ID */
|
---|
567 | return XZ_OPTIONS_ERROR;
|
---|
568 | }
|
---|
569 |
|
---|
570 | s->type = id;
|
---|
571 | s->ret = XZ_OK;
|
---|
572 | s->pos = 0;
|
---|
573 | s->x86_prev_mask = 0;
|
---|
574 | s->temp.filtered = 0;
|
---|
575 | s->temp.size = 0;
|
---|
576 |
|
---|
577 | return XZ_OK;
|
---|
578 | }
|
---|
579 |
|
---|
580 | #endif
|
---|