276 lines
7.7 KiB
C
276 lines
7.7 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 <dlfcn.h>
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#include <pthread.h>
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#include <stdio.h>
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#include "linker.h"
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#include "linker_format.h"
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/* This file hijacks the symbols stubbed out in libdl.so. */
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#define DL_SUCCESS 0
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#define DL_ERR_CANNOT_LOAD_LIBRARY 1
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#define DL_ERR_INVALID_LIBRARY_HANDLE 2
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#define DL_ERR_BAD_SYMBOL_NAME 3
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#define DL_ERR_SYMBOL_NOT_FOUND 4
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#define DL_ERR_SYMBOL_NOT_GLOBAL 5
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static char dl_err_buf[1024];
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static const char *dl_err_str;
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static const char *dl_errors[] = {
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[DL_ERR_CANNOT_LOAD_LIBRARY] = "Cannot load library",
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[DL_ERR_INVALID_LIBRARY_HANDLE] = "Invalid library handle",
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[DL_ERR_BAD_SYMBOL_NAME] = "Invalid symbol name",
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[DL_ERR_SYMBOL_NOT_FOUND] = "Symbol not found",
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[DL_ERR_SYMBOL_NOT_GLOBAL] = "Symbol is not global",
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};
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#define likely(expr) __builtin_expect (expr, 1)
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#define unlikely(expr) __builtin_expect (expr, 0)
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static pthread_mutex_t dl_lock = PTHREAD_MUTEX_INITIALIZER;
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static void set_dlerror(int err)
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{
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format_buffer(dl_err_buf, sizeof(dl_err_buf), "%s: %s", dl_errors[err],
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linker_get_error());
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dl_err_str = (const char *)&dl_err_buf[0];
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};
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void *dlopen(const char *filename, int flag)
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{
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soinfo *ret;
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pthread_mutex_lock(&dl_lock);
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ret = find_library(filename);
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if (unlikely(ret == NULL)) {
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set_dlerror(DL_ERR_CANNOT_LOAD_LIBRARY);
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} else {
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ret->refcount++;
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}
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pthread_mutex_unlock(&dl_lock);
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return ret;
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}
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const char *dlerror(void)
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{
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const char *tmp = dl_err_str;
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dl_err_str = NULL;
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return (const char *)tmp;
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}
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void *dlsym(void *handle, const char *symbol)
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{
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soinfo *found;
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Elf32_Sym *sym;
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unsigned bind;
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pthread_mutex_lock(&dl_lock);
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if(unlikely(handle == 0)) {
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set_dlerror(DL_ERR_INVALID_LIBRARY_HANDLE);
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goto err;
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}
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if(unlikely(symbol == 0)) {
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set_dlerror(DL_ERR_BAD_SYMBOL_NAME);
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goto err;
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}
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if(handle == RTLD_DEFAULT) {
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sym = 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 = lookup(symbol, &found, si->next);
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}
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} else {
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found = (soinfo*)handle;
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sym = lookup_in_library(found, symbol);
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}
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if(likely(sym != 0)) {
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bind = ELF32_ST_BIND(sym->st_info);
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if(likely((bind == STB_GLOBAL) && (sym->st_shndx != 0))) {
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unsigned ret = sym->st_value + found->base;
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pthread_mutex_unlock(&dl_lock);
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return (void*)ret;
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}
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set_dlerror(DL_ERR_SYMBOL_NOT_GLOBAL);
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}
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else
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set_dlerror(DL_ERR_SYMBOL_NOT_FOUND);
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err:
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pthread_mutex_unlock(&dl_lock);
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return 0;
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}
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int dladdr(void *addr, Dl_info *info)
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{
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int ret = 0;
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pthread_mutex_lock(&dl_lock);
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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) {
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memset(info, 0, sizeof(Dl_info));
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info->dli_fname = si->name;
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info->dli_fbase = (void*)si->base;
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/* Determine if any symbol in the library contains the specified address */
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Elf32_Sym *sym = find_containing_symbol(addr, si);
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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 = (void*)(si->base + sym->st_value);
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}
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ret = 1;
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}
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pthread_mutex_unlock(&dl_lock);
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return ret;
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}
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int dlclose(void *handle)
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{
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pthread_mutex_lock(&dl_lock);
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(void)unload_library((soinfo*)handle);
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pthread_mutex_unlock(&dl_lock);
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return 0;
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}
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#if defined(ANDROID_ARM_LINKER)
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// 0000000 00011111 111112 22222222 2333333 333344444444445555555
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// 0123456 78901234 567890 12345678 9012345 678901234567890123456
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#define ANDROID_LIBDL_STRTAB \
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"dlopen\0dlclose\0dlsym\0dlerror\0dladdr\0dl_unwind_find_exidx\0"
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#elif defined(ANDROID_X86_LINKER)
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// 0000000 00011111 111112 22222222 2333333 3333444444444455
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// 0123456 78901234 567890 12345678 9012345 6789012345678901
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#define ANDROID_LIBDL_STRTAB \
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"dlopen\0dlclose\0dlsym\0dlerror\0dladdr\0dl_iterate_phdr\0"
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#elif defined(ANDROID_SH_LINKER)
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// 0000000 00011111 111112 22222222 2333333 3333444444444455
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// 0123456 78901234 567890 12345678 9012345 6789012345678901
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#define ANDROID_LIBDL_STRTAB \
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"dlopen\0dlclose\0dlsym\0dlerror\0dladdr\0dl_iterate_phdr\0"
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#else /* !defined(ANDROID_ARM_LINKER) && !defined(ANDROID_X86_LINKER) */
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#error Unsupported architecture. Only ARM and x86 are presently supported.
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#endif
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static Elf32_Sym libdl_symtab[] = {
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// total length of libdl_info.strtab, including trailing 0
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// This is actually the 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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{ st_name: sizeof(ANDROID_LIBDL_STRTAB) - 1,
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},
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{ st_name: 0, // starting index of the name in libdl_info.strtab
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st_value: (Elf32_Addr) &dlopen,
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st_info: STB_GLOBAL << 4,
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st_shndx: 1,
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},
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{ st_name: 7,
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st_value: (Elf32_Addr) &dlclose,
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st_info: STB_GLOBAL << 4,
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st_shndx: 1,
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},
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{ st_name: 15,
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st_value: (Elf32_Addr) &dlsym,
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st_info: STB_GLOBAL << 4,
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st_shndx: 1,
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},
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{ st_name: 21,
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st_value: (Elf32_Addr) &dlerror,
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st_info: STB_GLOBAL << 4,
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st_shndx: 1,
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},
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{ st_name: 29,
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st_value: (Elf32_Addr) &dladdr,
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st_info: STB_GLOBAL << 4,
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st_shndx: 1,
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},
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#ifdef ANDROID_ARM_LINKER
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{ st_name: 36,
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st_value: (Elf32_Addr) &dl_unwind_find_exidx,
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st_info: STB_GLOBAL << 4,
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st_shndx: 1,
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},
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#elif defined(ANDROID_X86_LINKER)
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{ st_name: 36,
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st_value: (Elf32_Addr) &dl_iterate_phdr,
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st_info: STB_GLOBAL << 4,
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st_shndx: 1,
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},
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#elif defined(ANDROID_SH_LINKER)
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{ st_name: 36,
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st_value: (Elf32_Addr) &dl_iterate_phdr,
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st_info: STB_GLOBAL << 4,
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st_shndx: 1,
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},
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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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* A search of the hash table will look through
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* libdl_symtab starting with index [1], then
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* use libdl_chains to find the next index to
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* look at. libdl_chains should be set up to
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* walk through every element in libdl_symtab,
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* and then end with 0 (sentinel value).
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*
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* I.e., libdl_chains should look like
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* { 0, 2, 3, ... N, 0 } where N is the number
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* of actual symbols, or nelems(libdl_symtab)-1
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* (since the first element of libdl_symtab is not
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* a real symbol).
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*
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* (see _elf_lookup())
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*
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* Note that adding any new symbols here requires
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* stubbing them out in libdl.
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*/
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static unsigned libdl_buckets[1] = { 1 };
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static unsigned libdl_chains[7] = { 0, 2, 3, 4, 5, 6, 0 };
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soinfo libdl_info = {
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name: "libdl.so",
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flags: FLAG_LINKED,
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strtab: ANDROID_LIBDL_STRTAB,
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symtab: libdl_symtab,
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nbucket: 1,
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nchain: 7,
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bucket: libdl_buckets,
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chain: libdl_chains,
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};
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