lh | 9ed821d | 2023-04-07 01:36:19 -0700 | [diff] [blame] | 1 | /* Support for reading /etc/ld.so.cache files written by Linux ldconfig. |
| 2 | Copyright (C) 1996-2015 Free Software Foundation, Inc. |
| 3 | This file is part of the GNU C Library. |
| 4 | |
| 5 | The GNU C Library is free software; you can redistribute it and/or |
| 6 | modify it under the terms of the GNU Lesser General Public |
| 7 | License as published by the Free Software Foundation; either |
| 8 | version 2.1 of the License, or (at your option) any later version. |
| 9 | |
| 10 | The GNU C Library is distributed in the hope that it will be useful, |
| 11 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| 13 | Lesser General Public License for more details. |
| 14 | |
| 15 | You should have received a copy of the GNU Lesser General Public |
| 16 | License along with the GNU C Library; if not, see |
| 17 | <http://www.gnu.org/licenses/>. */ |
| 18 | |
| 19 | #include <assert.h> |
| 20 | #include <unistd.h> |
| 21 | #include <ldsodefs.h> |
| 22 | #include <sys/mman.h> |
| 23 | #include <dl-cache.h> |
| 24 | #include <dl-procinfo.h> |
| 25 | #include <stdint.h> |
| 26 | #include <_itoa.h> |
| 27 | |
| 28 | #ifndef _DL_PLATFORMS_COUNT |
| 29 | # define _DL_PLATFORMS_COUNT 0 |
| 30 | #endif |
| 31 | |
| 32 | /* This is the starting address and the size of the mmap()ed file. */ |
| 33 | static struct cache_file *cache; |
| 34 | static struct cache_file_new *cache_new; |
| 35 | static size_t cachesize; |
| 36 | |
| 37 | /* 1 if cache_data + PTR points into the cache. */ |
| 38 | #define _dl_cache_verify_ptr(ptr) (ptr < cache_data_size) |
| 39 | |
| 40 | #define SEARCH_CACHE(cache) \ |
| 41 | /* We use binary search since the table is sorted in the cache file. \ |
| 42 | The first matching entry in the table is returned. \ |
| 43 | It is important to use the same algorithm as used while generating \ |
| 44 | the cache file. */ \ |
| 45 | do \ |
| 46 | { \ |
| 47 | left = 0; \ |
| 48 | right = cache->nlibs - 1; \ |
| 49 | \ |
| 50 | while (left <= right) \ |
| 51 | { \ |
| 52 | __typeof__ (cache->libs[0].key) key; \ |
| 53 | \ |
| 54 | middle = (left + right) / 2; \ |
| 55 | \ |
| 56 | key = cache->libs[middle].key; \ |
| 57 | \ |
| 58 | /* Make sure string table indices are not bogus before using \ |
| 59 | them. */ \ |
| 60 | if (! _dl_cache_verify_ptr (key)) \ |
| 61 | { \ |
| 62 | cmpres = 1; \ |
| 63 | break; \ |
| 64 | } \ |
| 65 | \ |
| 66 | /* Actually compare the entry with the key. */ \ |
| 67 | cmpres = _dl_cache_libcmp (name, cache_data + key); \ |
| 68 | if (__glibc_unlikely (cmpres == 0)) \ |
| 69 | { \ |
| 70 | /* Found it. LEFT now marks the last entry for which we \ |
| 71 | know the name is correct. */ \ |
| 72 | left = middle; \ |
| 73 | \ |
| 74 | /* There might be entries with this name before the one we \ |
| 75 | found. So we have to find the beginning. */ \ |
| 76 | while (middle > 0) \ |
| 77 | { \ |
| 78 | __typeof__ (cache->libs[0].key) key; \ |
| 79 | \ |
| 80 | key = cache->libs[middle - 1].key; \ |
| 81 | /* Make sure string table indices are not bogus before \ |
| 82 | using them. */ \ |
| 83 | if (! _dl_cache_verify_ptr (key) \ |
| 84 | /* Actually compare the entry. */ \ |
| 85 | || _dl_cache_libcmp (name, cache_data + key) != 0) \ |
| 86 | break; \ |
| 87 | --middle; \ |
| 88 | } \ |
| 89 | \ |
| 90 | do \ |
| 91 | { \ |
| 92 | int flags; \ |
| 93 | __typeof__ (cache->libs[0]) *lib = &cache->libs[middle]; \ |
| 94 | \ |
| 95 | /* Only perform the name test if necessary. */ \ |
| 96 | if (middle > left \ |
| 97 | /* We haven't seen this string so far. Test whether the \ |
| 98 | index is ok and whether the name matches. Otherwise \ |
| 99 | we are done. */ \ |
| 100 | && (! _dl_cache_verify_ptr (lib->key) \ |
| 101 | || (_dl_cache_libcmp (name, cache_data + lib->key) \ |
| 102 | != 0))) \ |
| 103 | break; \ |
| 104 | \ |
| 105 | flags = lib->flags; \ |
| 106 | if (_dl_cache_check_flags (flags) \ |
| 107 | && _dl_cache_verify_ptr (lib->value)) \ |
| 108 | { \ |
| 109 | if (best == NULL || flags == GLRO(dl_correct_cache_id)) \ |
| 110 | { \ |
| 111 | HWCAP_CHECK; \ |
| 112 | best = cache_data + lib->value; \ |
| 113 | \ |
| 114 | if (flags == GLRO(dl_correct_cache_id)) \ |
| 115 | /* We've found an exact match for the shared \ |
| 116 | object and no general `ELF' release. Stop \ |
| 117 | searching. */ \ |
| 118 | break; \ |
| 119 | } \ |
| 120 | } \ |
| 121 | } \ |
| 122 | while (++middle <= right); \ |
| 123 | break; \ |
| 124 | } \ |
| 125 | \ |
| 126 | if (cmpres < 0) \ |
| 127 | left = middle + 1; \ |
| 128 | else \ |
| 129 | right = middle - 1; \ |
| 130 | } \ |
| 131 | } \ |
| 132 | while (0) |
| 133 | |
| 134 | |
| 135 | int |
| 136 | internal_function |
| 137 | _dl_cache_libcmp (const char *p1, const char *p2) |
| 138 | { |
| 139 | while (*p1 != '\0') |
| 140 | { |
| 141 | if (*p1 >= '0' && *p1 <= '9') |
| 142 | { |
| 143 | if (*p2 >= '0' && *p2 <= '9') |
| 144 | { |
| 145 | /* Must compare this numerically. */ |
| 146 | int val1; |
| 147 | int val2; |
| 148 | |
| 149 | val1 = *p1++ - '0'; |
| 150 | val2 = *p2++ - '0'; |
| 151 | while (*p1 >= '0' && *p1 <= '9') |
| 152 | val1 = val1 * 10 + *p1++ - '0'; |
| 153 | while (*p2 >= '0' && *p2 <= '9') |
| 154 | val2 = val2 * 10 + *p2++ - '0'; |
| 155 | if (val1 != val2) |
| 156 | return val1 - val2; |
| 157 | } |
| 158 | else |
| 159 | return 1; |
| 160 | } |
| 161 | else if (*p2 >= '0' && *p2 <= '9') |
| 162 | return -1; |
| 163 | else if (*p1 != *p2) |
| 164 | return *p1 - *p2; |
| 165 | else |
| 166 | { |
| 167 | ++p1; |
| 168 | ++p2; |
| 169 | } |
| 170 | } |
| 171 | return *p1 - *p2; |
| 172 | } |
| 173 | |
| 174 | |
| 175 | /* Look up NAME in ld.so.cache and return the file name stored there, or null |
| 176 | if none is found. The cache is loaded if it was not already. If loading |
| 177 | the cache previously failed there will be no more attempts to load it. |
| 178 | The caller is responsible for freeing the returned string. The ld.so.cache |
| 179 | may be unmapped at any time by a completing recursive dlopen and |
| 180 | this function must take care that it does not return references to |
| 181 | any data in the mapping. */ |
| 182 | char * |
| 183 | internal_function |
| 184 | _dl_load_cache_lookup (const char *name) |
| 185 | { |
| 186 | int left, right, middle; |
| 187 | int cmpres; |
| 188 | const char *cache_data; |
| 189 | uint32_t cache_data_size; |
| 190 | const char *best; |
| 191 | |
| 192 | /* Print a message if the loading of libs is traced. */ |
| 193 | if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_LIBS)) |
| 194 | _dl_debug_printf (" search cache=%s\n", LD_SO_CACHE); |
| 195 | |
| 196 | if (cache == NULL) |
| 197 | { |
| 198 | /* Read the contents of the file. */ |
| 199 | void *file = _dl_sysdep_read_whole_file (LD_SO_CACHE, &cachesize, |
| 200 | PROT_READ); |
| 201 | |
| 202 | /* We can handle three different cache file formats here: |
| 203 | - the old libc5/glibc2.0/2.1 format |
| 204 | - the old format with the new format in it |
| 205 | - only the new format |
| 206 | The following checks if the cache contains any of these formats. */ |
| 207 | if (file != MAP_FAILED && cachesize > sizeof *cache |
| 208 | && memcmp (file, CACHEMAGIC, sizeof CACHEMAGIC - 1) == 0) |
| 209 | { |
| 210 | size_t offset; |
| 211 | /* Looks ok. */ |
| 212 | cache = file; |
| 213 | |
| 214 | /* Check for new version. */ |
| 215 | offset = ALIGN_CACHE (sizeof (struct cache_file) |
| 216 | + cache->nlibs * sizeof (struct file_entry)); |
| 217 | |
| 218 | cache_new = (struct cache_file_new *) ((void *) cache + offset); |
| 219 | if (cachesize < (offset + sizeof (struct cache_file_new)) |
| 220 | || memcmp (cache_new->magic, CACHEMAGIC_VERSION_NEW, |
| 221 | sizeof CACHEMAGIC_VERSION_NEW - 1) != 0) |
| 222 | cache_new = (void *) -1; |
| 223 | } |
| 224 | else if (file != MAP_FAILED && cachesize > sizeof *cache_new |
| 225 | && memcmp (file, CACHEMAGIC_VERSION_NEW, |
| 226 | sizeof CACHEMAGIC_VERSION_NEW - 1) == 0) |
| 227 | { |
| 228 | cache_new = file; |
| 229 | cache = file; |
| 230 | } |
| 231 | else |
| 232 | { |
| 233 | if (file != MAP_FAILED) |
| 234 | __munmap (file, cachesize); |
| 235 | cache = (void *) -1; |
| 236 | } |
| 237 | |
| 238 | assert (cache != NULL); |
| 239 | } |
| 240 | |
| 241 | if (cache == (void *) -1) |
| 242 | /* Previously looked for the cache file and didn't find it. */ |
| 243 | return NULL; |
| 244 | |
| 245 | best = NULL; |
| 246 | |
| 247 | if (cache_new != (void *) -1) |
| 248 | { |
| 249 | uint64_t platform; |
| 250 | |
| 251 | /* This is where the strings start. */ |
| 252 | cache_data = (const char *) cache_new; |
| 253 | |
| 254 | /* Now we can compute how large the string table is. */ |
| 255 | cache_data_size = (const char *) cache + cachesize - cache_data; |
| 256 | |
| 257 | platform = _dl_string_platform (GLRO(dl_platform)); |
| 258 | if (platform != (uint64_t) -1) |
| 259 | platform = 1ULL << platform; |
| 260 | |
| 261 | #define _DL_HWCAP_TLS_MASK (1LL << 63) |
| 262 | uint64_t hwcap_exclude = ~((GLRO(dl_hwcap) & GLRO(dl_hwcap_mask)) |
| 263 | | _DL_HWCAP_PLATFORM | _DL_HWCAP_TLS_MASK); |
| 264 | |
| 265 | /* Only accept hwcap if it's for the right platform. */ |
| 266 | #define HWCAP_CHECK \ |
| 267 | if (lib->hwcap & hwcap_exclude) \ |
| 268 | continue; \ |
| 269 | if (GLRO(dl_osversion) && lib->osversion > GLRO(dl_osversion)) \ |
| 270 | continue; \ |
| 271 | if (_DL_PLATFORMS_COUNT \ |
| 272 | && (lib->hwcap & _DL_HWCAP_PLATFORM) != 0 \ |
| 273 | && (lib->hwcap & _DL_HWCAP_PLATFORM) != platform) \ |
| 274 | continue |
| 275 | SEARCH_CACHE (cache_new); |
| 276 | } |
| 277 | else |
| 278 | { |
| 279 | /* This is where the strings start. */ |
| 280 | cache_data = (const char *) &cache->libs[cache->nlibs]; |
| 281 | |
| 282 | /* Now we can compute how large the string table is. */ |
| 283 | cache_data_size = (const char *) cache + cachesize - cache_data; |
| 284 | |
| 285 | #undef HWCAP_CHECK |
| 286 | #define HWCAP_CHECK do {} while (0) |
| 287 | SEARCH_CACHE (cache); |
| 288 | } |
| 289 | |
| 290 | /* Print our result if wanted. */ |
| 291 | if (__builtin_expect (GLRO(dl_debug_mask) & DL_DEBUG_LIBS, 0) |
| 292 | && best != NULL) |
| 293 | _dl_debug_printf (" trying file=%s\n", best); |
| 294 | |
| 295 | if (best == NULL) |
| 296 | return NULL; |
| 297 | |
| 298 | /* The double copy is *required* since malloc may be interposed |
| 299 | and call dlopen itself whose completion would unmap the data |
| 300 | we are accessing. Therefore we must make the copy of the |
| 301 | mapping data without using malloc. */ |
| 302 | char *temp; |
| 303 | temp = alloca (strlen (best) + 1); |
| 304 | strcpy (temp, best); |
| 305 | return strdup (temp); |
| 306 | } |
| 307 | |
| 308 | #ifndef MAP_COPY |
| 309 | /* If the system does not support MAP_COPY we cannot leave the file open |
| 310 | all the time since this would create problems when the file is replaced. |
| 311 | Therefore we provide this function to close the file and open it again |
| 312 | once needed. */ |
| 313 | void |
| 314 | _dl_unload_cache (void) |
| 315 | { |
| 316 | if (cache != NULL && cache != (struct cache_file *) -1) |
| 317 | { |
| 318 | __munmap (cache, cachesize); |
| 319 | cache = NULL; |
| 320 | } |
| 321 | } |
| 322 | #endif |