1 | /*- |
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2 | * Copyright (c) 2013, Joseph Koshy |
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3 | * All rights reserved. |
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4 | * |
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5 | * Redistribution and use in source and binary forms, with or without |
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6 | * modification, are permitted provided that the following conditions |
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7 | * are met: |
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8 | * 1. Redistributions of source code must retain the above copyright |
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9 | * notice, this list of conditions and the following disclaimer |
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10 | * in this position and unchanged. |
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11 | * 2. Redistributions in binary form must reproduce the above copyright |
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12 | * notice, this list of conditions and the following disclaimer in the |
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13 | * documentation and/or other materials provided with the distribution. |
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14 | * |
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15 | * THIS SOFTWARE IS PROVIDED BY THE AUTHOR(S) ``AS IS'' AND ANY EXPRESS OR |
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16 | * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES |
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17 | * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. |
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18 | * IN NO EVENT SHALL THE AUTHOR(S) BE LIABLE FOR ANY DIRECT, INDIRECT, |
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19 | * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT |
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20 | * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
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21 | * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
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22 | * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
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23 | * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF |
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24 | * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
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25 | */ |
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26 | |
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27 | #include <sys/param.h> |
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28 | #include <sys/queue.h> |
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29 | |
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30 | #include <assert.h> |
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31 | #include <errno.h> |
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32 | #include <gelf.h> |
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33 | #include <stdlib.h> |
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34 | #include <string.h> |
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35 | |
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36 | #include "libelftc.h" |
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37 | #include "_libelftc.h" |
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38 | |
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39 | ELFTC_VCSID("$Id: elftc_string_table.c 2869 2013-01-06 13:29:18Z jkoshy $"); |
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40 | |
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41 | #define ELFTC_STRING_TABLE_DEFAULT_SIZE (4*1024) |
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42 | #define ELFTC_STRING_TABLE_EXPECTED_STRING_SIZE 16 |
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43 | #define ELFTC_STRING_TABLE_EXPECTED_CHAIN_LENGTH 8 |
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44 | #define ELFTC_STRING_TABLE_POOL_SIZE_INCREMENT (4*1024) |
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45 | |
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46 | struct _Elftc_String_Table_Entry { |
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47 | int ste_idx; |
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48 | SLIST_ENTRY(_Elftc_String_Table_Entry) ste_next; |
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49 | }; |
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50 | |
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51 | #define ELFTC_STRING_TABLE_COMPACTION_FLAG 0x1 |
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52 | #define ELFTC_STRING_TABLE_LENGTH(st) ((st)->st_len >> 1) |
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53 | #define ELFTC_STRING_TABLE_CLEAR_COMPACTION_FLAG(st) do { \ |
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54 | (st)->st_len &= ~ELFTC_STRING_TABLE_COMPACTION_FLAG; \ |
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55 | } while (0) |
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56 | #define ELFTC_STRING_TABLE_SET_COMPACTION_FLAG(st) do { \ |
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57 | (st)->st_len |= ELFTC_STRING_TABLE_COMPACTION_FLAG; \ |
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58 | } while (0) |
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59 | #define ELFTC_STRING_TABLE_UPDATE_LENGTH(st, len) do { \ |
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60 | (st)->st_len = \ |
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61 | ((st)->st_len & \ |
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62 | ELFTC_STRING_TABLE_COMPACTION_FLAG) | \ |
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63 | ((len) << 1); \ |
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64 | } while (0) |
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65 | |
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66 | struct _Elftc_String_Table { |
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67 | unsigned int st_len; /* length and flags */ |
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68 | int st_nbuckets; |
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69 | int st_string_pool_size; |
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70 | char *st_string_pool; |
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71 | SLIST_HEAD(_Elftc_String_Table_Bucket, |
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72 | _Elftc_String_Table_Entry) st_buckets[]; |
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73 | }; |
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74 | |
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75 | static struct _Elftc_String_Table_Entry * |
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76 | elftc_string_table_find_hash_entry(Elftc_String_Table *st, const char *string, |
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77 | int *rhashindex) |
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78 | { |
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79 | struct _Elftc_String_Table_Entry *ste; |
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80 | int hashindex; |
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81 | char *s; |
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82 | |
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83 | hashindex = libelftc_hash_string(string) % st->st_nbuckets; |
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84 | |
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85 | if (rhashindex) |
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86 | *rhashindex = hashindex; |
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87 | |
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88 | SLIST_FOREACH(ste, &st->st_buckets[hashindex], ste_next) { |
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89 | s = st->st_string_pool + abs(ste->ste_idx); |
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90 | |
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91 | assert(s > st->st_string_pool && |
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92 | s < st->st_string_pool + st->st_string_pool_size); |
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93 | |
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94 | if (strcmp(s, string) == 0) |
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95 | return (ste); |
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96 | } |
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97 | |
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98 | return (NULL); |
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99 | } |
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100 | |
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101 | static int |
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102 | elftc_string_table_add_to_pool(Elftc_String_Table *st, const char *string) |
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103 | { |
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104 | char *newpool; |
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105 | int len, newsize, stlen; |
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106 | |
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107 | len = strlen(string) + 1; /* length, including the trailing NUL */ |
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108 | stlen = ELFTC_STRING_TABLE_LENGTH(st); |
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109 | |
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110 | /* Resize the pool, if needed. */ |
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111 | if (stlen + len >= st->st_string_pool_size) { |
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112 | newsize = roundup(st->st_string_pool_size + |
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113 | ELFTC_STRING_TABLE_POOL_SIZE_INCREMENT, |
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114 | ELFTC_STRING_TABLE_POOL_SIZE_INCREMENT); |
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115 | if ((newpool = realloc(st->st_string_pool, newsize)) == |
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116 | NULL) |
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117 | return (0); |
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118 | st->st_string_pool = newpool; |
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119 | st->st_string_pool_size = newsize; |
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120 | } |
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121 | |
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122 | strcpy(st->st_string_pool + stlen, string); |
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123 | ELFTC_STRING_TABLE_UPDATE_LENGTH(st, stlen + len); |
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124 | |
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125 | return (stlen); |
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126 | } |
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127 | |
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128 | Elftc_String_Table * |
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129 | elftc_string_table_create(int sizehint) |
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130 | { |
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131 | int n, nbuckets, tablesize; |
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132 | struct _Elftc_String_Table *st; |
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133 | |
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134 | if (sizehint < ELFTC_STRING_TABLE_DEFAULT_SIZE) |
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135 | sizehint = ELFTC_STRING_TABLE_DEFAULT_SIZE; |
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136 | |
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137 | nbuckets = sizehint / (ELFTC_STRING_TABLE_EXPECTED_CHAIN_LENGTH * |
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138 | ELFTC_STRING_TABLE_EXPECTED_STRING_SIZE); |
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139 | |
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140 | tablesize = sizeof(struct _Elftc_String_Table) + |
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141 | nbuckets * sizeof(struct _Elftc_String_Table_Bucket); |
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142 | |
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143 | if ((st = malloc(tablesize)) == NULL) |
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144 | return (NULL); |
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145 | if ((st->st_string_pool = malloc(sizehint)) == NULL) { |
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146 | free(st); |
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147 | return (NULL); |
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148 | } |
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149 | |
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150 | for (n = 0; n < nbuckets; n++) |
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151 | SLIST_INIT(&st->st_buckets[n]); |
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152 | |
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153 | st->st_len = 0; |
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154 | st->st_nbuckets = nbuckets; |
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155 | st->st_string_pool_size = sizehint; |
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156 | *st->st_string_pool = '\0'; |
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157 | ELFTC_STRING_TABLE_UPDATE_LENGTH(st, 1); |
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158 | |
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159 | return (st); |
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160 | } |
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161 | |
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162 | void |
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163 | elftc_string_table_destroy(Elftc_String_Table *st) |
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164 | { |
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165 | int n; |
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166 | struct _Elftc_String_Table_Entry *s, *t; |
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167 | |
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168 | for (n = 0; n < st->st_nbuckets; n++) |
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169 | SLIST_FOREACH_SAFE(s, &st->st_buckets[n], ste_next, t) |
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170 | free(s); |
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171 | free(st->st_string_pool); |
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172 | free(st); |
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173 | |
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174 | return; |
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175 | } |
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176 | |
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177 | Elftc_String_Table * |
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178 | elftc_string_table_from_section(Elf_Scn *scn, int sizehint) |
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179 | { |
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180 | int len; |
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181 | Elf_Data *d; |
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182 | GElf_Shdr sh; |
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183 | const char *s, *end; |
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184 | Elftc_String_Table *st; |
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185 | |
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186 | /* Verify the type of the section passed in. */ |
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187 | if (gelf_getshdr(scn, &sh) == NULL || |
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188 | sh.sh_type != SHT_STRTAB) { |
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189 | errno = EINVAL; |
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190 | return (NULL); |
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191 | } |
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192 | |
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193 | if ((d = elf_getdata(scn, NULL)) == NULL || |
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194 | d->d_size == 0) { |
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195 | errno = EINVAL; |
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196 | return (NULL); |
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197 | } |
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198 | |
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199 | if ((st = elftc_string_table_create(sizehint)) == NULL) |
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200 | return (NULL); |
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201 | |
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202 | s = d->d_buf; |
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203 | |
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204 | /* |
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205 | * Verify that the first byte of the data buffer is '\0'. |
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206 | */ |
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207 | if (*s != '\0') { |
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208 | errno = EINVAL; |
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209 | goto fail; |
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210 | } |
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211 | |
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212 | end = s + d->d_size; |
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213 | |
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214 | /* |
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215 | * Skip the first '\0' and insert the strings in the buffer, |
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216 | * in order. |
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217 | */ |
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218 | for (s += 1; s < end; s += len) { |
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219 | if (elftc_string_table_insert(st, s) == 0) |
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220 | goto fail; |
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221 | |
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222 | len = strlen(s) + 1; /* Include space for the trailing NUL. */ |
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223 | } |
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224 | |
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225 | return (st); |
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226 | |
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227 | fail: |
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228 | if (st) |
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229 | (void) elftc_string_table_destroy(st); |
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230 | |
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231 | return (NULL); |
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232 | } |
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233 | |
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234 | const char * |
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235 | elftc_string_table_image(Elftc_String_Table *st, size_t *size) |
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236 | { |
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237 | char *r, *s, *end; |
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238 | struct _Elftc_String_Table_Entry *ste; |
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239 | struct _Elftc_String_Table_Bucket *head; |
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240 | int copied, hashindex, offset, length, newsize; |
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241 | |
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242 | /* |
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243 | * For the common case of a string table has not seen |
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244 | * a string deletion, we can just export the current |
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245 | * pool. |
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246 | */ |
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247 | if ((st->st_len & ELFTC_STRING_TABLE_COMPACTION_FLAG) == 0) { |
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248 | if (size) |
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249 | *size = ELFTC_STRING_TABLE_LENGTH(st); |
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250 | return (st->st_string_pool); |
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251 | } |
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252 | |
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253 | /* |
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254 | * Otherwise, compact the string table in-place. |
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255 | */ |
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256 | assert(*st->st_string_pool == '\0'); |
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257 | |
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258 | newsize = 1; |
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259 | end = st->st_string_pool + ELFTC_STRING_TABLE_LENGTH(st); |
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260 | |
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261 | for (r = s = st->st_string_pool + 1; |
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262 | s < end; |
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263 | s += length, r += copied) { |
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264 | |
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265 | copied = 0; |
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266 | length = strlen(s) + 1; |
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267 | |
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268 | ste = elftc_string_table_find_hash_entry(st, s, |
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269 | &hashindex); |
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270 | head = &st->st_buckets[hashindex]; |
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271 | |
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272 | assert(ste != NULL); |
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273 | |
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274 | /* Ignore deleted strings. */ |
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275 | if (ste->ste_idx < 0) { |
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276 | SLIST_REMOVE(head, ste, _Elftc_String_Table_Entry, |
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277 | ste_next); |
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278 | free(ste); |
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279 | continue; |
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280 | } |
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281 | |
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282 | /* Move 'live' strings up. */ |
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283 | offset = newsize; |
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284 | newsize += length; |
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285 | copied = length; |
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286 | |
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287 | if (r == s) /* Nothing removed yet. */ |
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288 | continue; |
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289 | |
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290 | memmove(r, s, copied); |
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291 | |
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292 | /* Update the index for this entry. */ |
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293 | ste->ste_idx = offset; |
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294 | } |
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295 | |
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296 | ELFTC_STRING_TABLE_CLEAR_COMPACTION_FLAG(st); |
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297 | ELFTC_STRING_TABLE_UPDATE_LENGTH(st, newsize); |
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298 | |
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299 | if (size) |
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300 | *size = newsize; |
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301 | |
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302 | return (st->st_string_pool); |
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303 | } |
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304 | |
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305 | size_t |
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306 | elftc_string_table_insert(Elftc_String_Table *st, const char *string) |
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307 | { |
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308 | int hashindex, idx; |
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309 | struct _Elftc_String_Table_Entry *ste; |
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310 | |
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311 | hashindex = 0; |
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312 | |
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313 | ste = elftc_string_table_find_hash_entry(st, string, &hashindex); |
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314 | |
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315 | assert(hashindex >= 0 && hashindex < st->st_nbuckets); |
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316 | |
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317 | if (ste == NULL) { |
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318 | if ((ste = malloc(sizeof(*ste))) == NULL) |
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319 | return (0); |
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320 | if ((ste->ste_idx = elftc_string_table_add_to_pool(st, |
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321 | string)) == 0) { |
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322 | free(ste); |
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323 | return (0); |
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324 | } |
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325 | |
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326 | SLIST_INSERT_HEAD(&st->st_buckets[hashindex], ste, ste_next); |
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327 | } |
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328 | |
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329 | idx = ste->ste_idx; |
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330 | if (idx < 0) /* Undelete. */ |
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331 | ste->ste_idx = idx = (- idx); |
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332 | |
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333 | return (idx); |
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334 | } |
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335 | |
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336 | size_t |
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337 | elftc_string_table_lookup(Elftc_String_Table *st, const char *string) |
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338 | { |
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339 | int hashindex, idx; |
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340 | struct _Elftc_String_Table_Entry *ste; |
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341 | |
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342 | ste = elftc_string_table_find_hash_entry(st, string, &hashindex); |
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343 | |
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344 | assert(hashindex >= 0 && hashindex < st->st_nbuckets); |
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345 | |
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346 | if (ste == NULL || (idx = ste->ste_idx) < 0) |
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347 | return (0); |
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348 | |
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349 | return (idx); |
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350 | } |
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351 | |
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352 | int |
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353 | elftc_string_table_remove(Elftc_String_Table *st, const char *string) |
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354 | { |
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355 | int idx; |
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356 | struct _Elftc_String_Table_Entry *ste; |
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357 | |
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358 | ste = elftc_string_table_find_hash_entry(st, string, NULL); |
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359 | |
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360 | if (ste == NULL || (idx = ste->ste_idx) < 0) |
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361 | return (ELFTC_FAILURE); |
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362 | |
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363 | assert(idx > 0 && idx < (int) ELFTC_STRING_TABLE_LENGTH(st)); |
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364 | |
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365 | ste->ste_idx = (- idx); |
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366 | |
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367 | ELFTC_STRING_TABLE_SET_COMPACTION_FLAG(st); |
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368 | |
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369 | return (ELFTC_SUCCESS); |
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370 | } |
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371 | |
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372 | const char * |
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373 | elftc_string_table_to_string(Elftc_String_Table *st, size_t offset) |
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374 | { |
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375 | const char *s; |
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376 | |
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377 | s = st->st_string_pool + offset; |
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378 | |
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379 | /* |
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380 | * Check for: |
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381 | * - An offset value within pool bounds. |
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382 | * - A non-NUL byte at the specified offset. |
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383 | * - The end of the prior string at offset - 1. |
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384 | */ |
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385 | if (offset == 0 || offset >= ELFTC_STRING_TABLE_LENGTH(st) || |
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386 | *s == '\0' || *(s - 1) != '\0') { |
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387 | errno = EINVAL; |
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388 | return (NULL); |
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389 | } |
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390 | |
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391 | return (s); |
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392 | } |
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