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jeremybenn |
/* Support for reading /etc/ld.so.cache files written by Linux ldconfig.
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Copyright (C) 1996,1997,1998,1999,2000,2001 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, write to the Free
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Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
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02111-1307 USA. */
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#include <assert.h>
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#include <unistd.h>
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#include <ldsodefs.h>
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#include <sys/mman.h>
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#include <dl-cache.h>
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#include <machine/dl-procinfo.h>
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#include <machine/weakalias.h>
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extern const char *_dl_platform;
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#ifndef _DL_PLATFORMS_COUNT
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# define _DL_PLATFORMS_COUNT 0
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#endif
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/* This is the starting address and the size of the mmap()ed file. */
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static struct cache_file *cache;
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static struct cache_file_new *cache_new;
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static size_t cachesize;
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/* 1 if cache_data + PTR points into the cache. */
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#define _dl_cache_verify_ptr(ptr) (ptr < cache_data_size)
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/* This is the cache ID we expect. Normally it is 3 for glibc linked
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binaries. */
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int _dl_correct_cache_id = _DL_CACHE_DEFAULT_ID;
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#define SEARCH_CACHE(cache) \
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/* We use binary search since the table is sorted in the cache file. \
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The first matching entry in the table is returned. \
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It is important to use the same algorithm as used while generating \
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the cache file. */ \
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do \
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{ \
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left = 0; \
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right = cache->nlibs - 1; \
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\
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while (left <= right) \
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{ \
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__typeof__ (cache->libs[0].key) key; \
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\
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middle = (left + right) / 2; \
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\
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key = cache->libs[middle].key; \
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\
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/* Make sure string table indices are not bogus before using \
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them. */ \
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if (! _dl_cache_verify_ptr (key)) \
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{ \
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cmpres = 1; \
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break; \
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} \
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\
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/* Actually compare the entry with the key. */ \
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cmpres = _dl_cache_libcmp (name, cache_data + key); \
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if (__builtin_expect (cmpres == 0, 0)) \
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{ \
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/* Found it. LEFT now marks the last entry for which we \
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know the name is correct. */ \
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left = middle; \
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\
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/* There might be entries with this name before the one we \
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found. So we have to find the beginning. */ \
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while (middle > 0) \
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{ \
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__typeof__ (cache->libs[0].key) key; \
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\
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key = cache->libs[middle - 1].key; \
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/* Make sure string table indices are not bogus before \
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using them. */ \
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if (! _dl_cache_verify_ptr (key) \
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/* Actually compare the entry. */ \
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|| _dl_cache_libcmp (name, cache_data + key) != 0) \
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break; \
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--middle; \
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} \
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\
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do \
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{ \
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int flags; \
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__typeof__ (cache->libs[0]) *lib = &cache->libs[middle]; \
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\
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/* Only perform the name test if necessary. */ \
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if (middle > left \
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/* We haven't seen this string so far. Test whether the \
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index is ok and whether the name matches. Otherwise \
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we are done. */ \
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&& (! _dl_cache_verify_ptr (lib->key) \
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|| (_dl_cache_libcmp (name, cache_data + lib->key) \
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!= 0))) \
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break; \
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\
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flags = lib->flags; \
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if (_dl_cache_check_flags (flags) \
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&& _dl_cache_verify_ptr (lib->value)) \
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{ \
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if (best == NULL || flags == _dl_correct_cache_id) \
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{ \
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HWCAP_CHECK; \
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best = cache_data + lib->value; \
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\
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if (flags == _dl_correct_cache_id) \
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/* We've found an exact match for the shared \
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object and no general `ELF' release. Stop \
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searching. */ \
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break; \
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} \
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} \
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} \
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while (++middle <= right); \
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break; \
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} \
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\
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if (cmpres < 0) \
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left = middle + 1; \
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else \
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right = middle - 1; \
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} \
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} \
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while (0)
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/* Look up NAME in ld.so.cache and return the file name stored there,
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or null if none is found. */
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const char *
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internal_function
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_dl_load_cache_lookup (const char *name)
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{
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int left, right, middle;
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int cmpres;
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const char *cache_data;
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uint32_t cache_data_size;
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const char *best;
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if (cache == NULL)
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{
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/* Read the contents of the file. */
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void *file = _dl_sysdep_read_whole_file (LD_SO_CACHE, &cachesize,
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PROT_READ);
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/* We can handle three different cache file formats here:
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- the old libc5/glibc2.0/2.1 format
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- the old format with the new format in it
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- only the new format
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The following checks if the cache contains any of these formats. */
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if (file != MAP_FAILED && cachesize > sizeof *cache
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&& memcmp (file, CACHEMAGIC, sizeof CACHEMAGIC - 1) == 0)
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{
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size_t offset;
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/* Looks ok. */
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cache = file;
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/* Check for new version. */
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offset = ALIGN_CACHE (sizeof (struct cache_file)
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+ cache->nlibs * sizeof (struct file_entry));
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cache_new = (struct cache_file_new *) ((void *) cache + offset);
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if (cachesize < (offset + sizeof (struct cache_file_new))
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|| memcmp (cache_new->magic, CACHEMAGIC_VERSION_NEW,
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sizeof CACHEMAGIC_VERSION_NEW - 1) != 0)
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cache_new = (void *) -1;
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}
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else if (file != MAP_FAILED && cachesize > sizeof *cache_new
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&& memcmp (file, CACHEMAGIC_VERSION_NEW,
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sizeof CACHEMAGIC_VERSION_NEW - 1) == 0)
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{
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cache_new = file;
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cache = file;
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}
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else
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{
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if (file != MAP_FAILED)
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munmap (file, cachesize);
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cache = (void *) -1;
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}
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assert (cache != NULL);
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}
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if (cache == (void *) -1)
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/* Previously looked for the cache file and didn't find it. */
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return NULL;
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best = NULL;
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if (cache_new != (void *) -1)
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{
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/* This file ends in static libraries where we don't have a hwcap. */
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unsigned long int *hwcap;
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uint64_t platform;
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#pragma weak _dl_hwcap
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/* This is where the strings start. */
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cache_data = (const char *) cache_new;
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/* Now we can compute how large the string table is. */
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cache_data_size = (const char *) cache + cachesize - cache_data;
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hwcap = &_dl_hwcap;
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platform = _dl_string_platform (_dl_platform);
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if (platform != -1)
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platform = 1ULL << platform;
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/* Only accept hwcap if it's for the right platform. */
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#define HWCAP_CHECK \
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if (_dl_osversion && cache_new->libs[middle].osversion > _dl_osversion) \
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continue; \
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if (_DL_PLATFORMS_COUNT && platform != -1 \
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&& (lib->hwcap & _DL_HWCAP_PLATFORM) != 0 \
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&& (lib->hwcap & _DL_HWCAP_PLATFORM) != platform) \
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continue; \
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if (hwcap \
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&& ((lib->hwcap & *hwcap & ~_DL_HWCAP_PLATFORM) > *hwcap)) \
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continue
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SEARCH_CACHE (cache_new);
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}
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else
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{
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/* This is where the strings start. */
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cache_data = (const char *) &cache->libs[cache->nlibs];
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/* Now we can compute how large the string table is. */
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cache_data_size = (const char *) cache + cachesize - cache_data;
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#undef HWCAP_CHECK
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#define HWCAP_CHECK do {} while (0)
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SEARCH_CACHE (cache);
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}
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/* Print our result if wanted. */
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if (__builtin_expect (_dl_debug_mask & DL_DEBUG_LIBS, 0) && best != NULL)
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_dl_debug_printf (" trying file=%s\n", best);
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return best;
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}
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#ifndef MAP_COPY
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/* If the system does not support MAP_COPY we cannot leave the file open
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all the time since this would create problems when the file is replaced.
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Therefore we provide this function to close the file and open it again
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once needed. */
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void
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_dl_unload_cache (void)
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{
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if (cache != NULL && cache != (struct cache_file *) -1)
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{
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munmap (cache, cachesize);
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cache = NULL;
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}
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}
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#endif
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