295 lines
8.9 KiB
C++
295 lines
8.9 KiB
C++
/*
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* Copyright (C) 2007 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include "linker.h"
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#include <dlfcn.h>
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#include <pthread.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <bionic/pthread_internal.h>
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#include "private/bionic_tls.h"
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#include "private/ScopedPthreadMutexLocker.h"
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#include "private/ThreadLocalBuffer.h"
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/* This file hijacks the symbols stubbed out in libdl.so. */
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static pthread_mutex_t gDlMutex = PTHREAD_RECURSIVE_MUTEX_INITIALIZER;
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static const char* __bionic_set_dlerror(char* new_value) {
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char** dlerror_slot = &reinterpret_cast<char**>(__get_tls())[TLS_SLOT_DLERROR];
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const char* old_value = *dlerror_slot;
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*dlerror_slot = new_value;
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return old_value;
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}
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static void __bionic_format_dlerror(const char* msg, const char* detail) {
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char* buffer = __get_thread()->dlerror_buffer;
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strlcpy(buffer, msg, __BIONIC_DLERROR_BUFFER_SIZE);
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if (detail != NULL) {
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strlcat(buffer, ": ", __BIONIC_DLERROR_BUFFER_SIZE);
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strlcat(buffer, detail, __BIONIC_DLERROR_BUFFER_SIZE);
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}
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__bionic_set_dlerror(buffer);
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}
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const char* dlerror() {
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const char* old_value = __bionic_set_dlerror(NULL);
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return old_value;
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}
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void android_get_LD_LIBRARY_PATH(char* buffer, size_t buffer_size) {
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ScopedPthreadMutexLocker locker(&gDlMutex);
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do_android_get_LD_LIBRARY_PATH(buffer, buffer_size);
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}
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void android_update_LD_LIBRARY_PATH(const char* ld_library_path) {
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ScopedPthreadMutexLocker locker(&gDlMutex);
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do_android_update_LD_LIBRARY_PATH(ld_library_path);
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}
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void* dlopen(const char* filename, int flags) {
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ScopedPthreadMutexLocker locker(&gDlMutex);
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soinfo* result = do_dlopen(filename, flags);
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if (result == NULL) {
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__bionic_format_dlerror("dlopen failed", linker_get_error_buffer());
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return NULL;
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}
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return result;
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}
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void* dlsym(void* handle, const char* symbol) {
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ScopedPthreadMutexLocker locker(&gDlMutex);
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if (handle == NULL) {
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__bionic_format_dlerror("dlsym library handle is null", NULL);
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return NULL;
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}
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if (symbol == NULL) {
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__bionic_format_dlerror("dlsym symbol name is null", NULL);
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return NULL;
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}
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soinfo* found = NULL;
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ElfW(Sym)* sym = NULL;
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if (handle == RTLD_DEFAULT) {
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sym = dlsym_linear_lookup(symbol, &found, NULL);
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} else if (handle == RTLD_NEXT) {
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void* ret_addr = __builtin_return_address(0);
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soinfo* si = find_containing_library(ret_addr);
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sym = NULL;
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if (si && si->next) {
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sym = dlsym_linear_lookup(symbol, &found, si->next);
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}
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} else {
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found = reinterpret_cast<soinfo*>(handle);
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sym = dlsym_handle_lookup(found, symbol);
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}
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if (sym != NULL) {
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unsigned bind = ELF_ST_BIND(sym->st_info);
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if (bind == STB_GLOBAL && sym->st_shndx != 0) {
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return reinterpret_cast<void*>(sym->st_value + found->load_bias);
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}
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__bionic_format_dlerror("symbol found but not global", symbol);
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return NULL;
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} else {
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__bionic_format_dlerror("undefined symbol", symbol);
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return NULL;
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}
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}
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int dladdr(const void* addr, Dl_info* info) {
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ScopedPthreadMutexLocker locker(&gDlMutex);
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// Determine if this address can be found in any library currently mapped.
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soinfo* si = find_containing_library(addr);
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if (si == NULL) {
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return 0;
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}
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memset(info, 0, sizeof(Dl_info));
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info->dli_fname = si->name;
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// Address at which the shared object is loaded.
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info->dli_fbase = reinterpret_cast<void*>(si->base);
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// Determine if any symbol in the library contains the specified address.
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ElfW(Sym)* sym = dladdr_find_symbol(si, addr);
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if (sym != NULL) {
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info->dli_sname = si->strtab + sym->st_name;
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info->dli_saddr = reinterpret_cast<void*>(si->load_bias + sym->st_value);
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}
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return 1;
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}
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int dlclose(void* handle) {
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ScopedPthreadMutexLocker locker(&gDlMutex);
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return do_dlclose(reinterpret_cast<soinfo*>(handle));
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}
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// name_offset: starting index of the name in libdl_info.strtab
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#define ELF32_SYM_INITIALIZER(name_offset, value, shndx) \
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{ name_offset, \
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reinterpret_cast<Elf32_Addr>(reinterpret_cast<void*>(value)), \
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/* st_size */ 0, \
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(shndx == 0) ? 0 : (STB_GLOBAL << 4), \
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/* st_other */ 0, \
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shndx, \
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}
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#define ELF64_SYM_INITIALIZER(name_offset, value, shndx) \
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{ name_offset, \
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(shndx == 0) ? 0 : (STB_GLOBAL << 4), \
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/* st_other */ 0, \
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shndx, \
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reinterpret_cast<Elf64_Addr>(reinterpret_cast<void*>(value)), \
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/* st_size */ 0, \
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}
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#if defined(__arm__)
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// 0000000 00011111 111112 22222222 2333333 3333444444444455555555556666666 6667777777777888888888899999 9999900000000001 1
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// 0123456 78901234 567890 12345678 9012345 6789012345678901234567890123456 7890123456789012345678901234 5678901234567890 1
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# define ANDROID_LIBDL_STRTAB \
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"dlopen\0dlclose\0dlsym\0dlerror\0dladdr\0android_update_LD_LIBRARY_PATH\0android_get_LD_LIBRARY_PATH\0dl_iterate_phdr\0dl_unwind_find_exidx\0"
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#elif defined(__aarch64__) || defined(__i386__) || defined(__mips__) || defined(__x86_64__)
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// 0000000 00011111 111112 22222222 2333333 3333444444444455555555556666666 6667777777777888888888899999 9999900000000001 1
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// 0123456 78901234 567890 12345678 9012345 6789012345678901234567890123456 7890123456789012345678901234 5678901234567890 1
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# define ANDROID_LIBDL_STRTAB \
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"dlopen\0dlclose\0dlsym\0dlerror\0dladdr\0android_update_LD_LIBRARY_PATH\0android_get_LD_LIBRARY_PATH\0dl_iterate_phdr\0"
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#else
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# error Unsupported architecture. Only arm, arm64, mips, mips64, x86 and x86_64 are presently supported.
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#endif
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static ElfW(Sym) gLibDlSymtab[] = {
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// Total length of libdl_info.strtab, including trailing 0.
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// This is actually the STH_UNDEF entry. Technically, it's
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// supposed to have st_name == 0, but instead, it points to an index
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// in the strtab with a \0 to make iterating through the symtab easier.
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ELFW(SYM_INITIALIZER)(sizeof(ANDROID_LIBDL_STRTAB) - 1, NULL, 0),
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ELFW(SYM_INITIALIZER)( 0, &dlopen, 1),
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ELFW(SYM_INITIALIZER)( 7, &dlclose, 1),
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ELFW(SYM_INITIALIZER)( 15, &dlsym, 1),
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ELFW(SYM_INITIALIZER)( 21, &dlerror, 1),
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ELFW(SYM_INITIALIZER)( 29, &dladdr, 1),
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ELFW(SYM_INITIALIZER)( 36, &android_update_LD_LIBRARY_PATH, 1),
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ELFW(SYM_INITIALIZER)( 67, &android_get_LD_LIBRARY_PATH, 1),
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ELFW(SYM_INITIALIZER)( 95, &dl_iterate_phdr, 1),
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#if defined(__arm__)
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ELFW(SYM_INITIALIZER)(111, &dl_unwind_find_exidx, 1),
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#endif
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};
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// Fake out a hash table with a single bucket.
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//
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// A search of the hash table will look through gLibDlSymtab starting with index 1, then
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// use gLibDlChains to find the next index to look at. gLibDlChains should be set up to
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// walk through every element in gLibDlSymtab, and then end with 0 (sentinel value).
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//
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// That is, gLibDlChains should look like { 0, 2, 3, ... N, 0 } where N is the number
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// of actual symbols, or nelems(gLibDlSymtab)-1 (since the first element of gLibDlSymtab is not
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// a real symbol). (See soinfo_elf_lookup().)
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//
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// Note that adding any new symbols here requires stubbing them out in libdl.
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static unsigned gLibDlBuckets[1] = { 1 };
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#if defined(__arm__)
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static unsigned gLibDlChains[] = { 0, 2, 3, 4, 5, 6, 7, 8, 9, 0 };
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#else
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static unsigned gLibDlChains[] = { 0, 2, 3, 4, 5, 6, 7, 8, 0 };
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#endif
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// This is used by the dynamic linker. Every process gets these symbols for free.
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soinfo libdl_info = {
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"libdl.so",
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.phdr = 0,
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.phnum = 0,
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.entry = 0,
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.base = 0,
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.size = 0,
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#if !defined(__LP64__)
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.unused1 = 0,
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#endif
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.dynamic = 0,
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#if !defined(__LP64__)
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.unused2 = 0, .unused3 = 0,
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#endif
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.next = 0,
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.flags = FLAG_LINKED,
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.strtab = ANDROID_LIBDL_STRTAB,
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.symtab = gLibDlSymtab,
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.nbucket = sizeof(gLibDlBuckets)/sizeof(unsigned),
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.nchain = sizeof(gLibDlChains)/sizeof(unsigned),
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.bucket = gLibDlBuckets,
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.chain = gLibDlChains,
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#if defined(USE_RELA)
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.plt_rela = 0,
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.plt_rela_count = 0,
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.rela = 0,
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.rela_count = 0,
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#else
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.plt_got = 0,
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.plt_rel = 0,
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.plt_rel_count = 0,
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.rel = 0,
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.rel_count = 0,
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#endif
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.preinit_array = 0,
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.preinit_array_count = 0,
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.init_array = 0,
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.init_array_count = 0,
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.fini_array = 0,
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.fini_array_count = 0,
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.init_func = 0,
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.fini_func = 0,
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#if defined(__arm__)
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.ARM_exidx = 0,
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.ARM_exidx_count = 0,
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#elif defined(__mips__)
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.mips_symtabno = 0,
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.mips_local_gotno = 0,
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.mips_gotsym = 0,
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#endif
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.ref_count = 0,
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{ .l_addr = 0, .l_name = 0, .l_ld = 0, .l_next = 0, .l_prev = 0, },
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.constructors_called = false,
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.load_bias = 0,
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#if !defined(__LP64__)
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.has_text_relocations = false,
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#endif
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.has_DT_SYMBOLIC = true,
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};
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