253 lines
9 KiB
C++
253 lines
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 <android/dlext.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 g_dl_mutex = PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP;
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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 != nullptr) {
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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(nullptr);
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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(&g_dl_mutex);
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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(&g_dl_mutex);
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do_android_update_LD_LIBRARY_PATH(ld_library_path);
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}
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static void* dlopen_ext(const char* filename, int flags, const android_dlextinfo* extinfo) {
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ScopedPthreadMutexLocker locker(&g_dl_mutex);
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soinfo* result = do_dlopen(filename, flags, extinfo);
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if (result == nullptr) {
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__bionic_format_dlerror("dlopen failed", linker_get_error_buffer());
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return nullptr;
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}
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return result;
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}
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void* android_dlopen_ext(const char* filename, int flags, const android_dlextinfo* extinfo) {
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return dlopen_ext(filename, flags, extinfo);
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}
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void* dlopen(const char* filename, int flags) {
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return dlopen_ext(filename, flags, nullptr);
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}
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void* dlsym(void* handle, const char* symbol) {
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ScopedPthreadMutexLocker locker(&g_dl_mutex);
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#if !defined(__LP64__)
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if (handle == nullptr) {
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__bionic_format_dlerror("dlsym library handle is null", nullptr);
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return nullptr;
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}
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#endif
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if (symbol == nullptr) {
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__bionic_format_dlerror("dlsym symbol name is null", nullptr);
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return nullptr;
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}
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soinfo* found = nullptr;
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ElfW(Sym)* sym = nullptr;
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if (handle == RTLD_DEFAULT) {
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sym = dlsym_linear_lookup(symbol, &found, nullptr);
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} else if (handle == RTLD_NEXT) {
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void* caller_addr = __builtin_return_address(0);
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soinfo* si = find_containing_library(caller_addr);
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sym = nullptr;
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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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sym = dlsym_handle_lookup(reinterpret_cast<soinfo*>(handle), &found, symbol);
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}
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if (sym != nullptr) {
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unsigned bind = ELF_ST_BIND(sym->st_info);
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if ((bind == STB_GLOBAL || bind == STB_WEAK) && sym->st_shndx != 0) {
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return reinterpret_cast<void*>(found->resolve_symbol_address(sym));
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}
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__bionic_format_dlerror("symbol found but not global", symbol);
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return nullptr;
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} else {
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__bionic_format_dlerror("undefined symbol", symbol);
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return nullptr;
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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(&g_dl_mutex);
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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 == nullptr) {
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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 = si->find_symbol_by_address(addr);
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if (sym != nullptr) {
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info->dli_sname = si->get_string(sym->st_name);
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info->dli_saddr = reinterpret_cast<void*>(si->resolve_symbol_address(sym));
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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(&g_dl_mutex);
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do_dlclose(reinterpret_cast<soinfo*>(handle));
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// dlclose has no defined errors.
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return 0;
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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>(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>(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 1111111112222222222 333333333344444444445
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// 0123456 78901234 567890 12345678 9012345 6789012345678901234567890123456 7890123456789012345678901234 5678901234567890 1234567890123456789 012345678901234567890
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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\0android_dlopen_ext\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 1111111112222222222
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// 0123456 78901234 567890 12345678 9012345 6789012345678901234567890123456 7890123456789012345678901234 5678901234567890 1234567890123456789
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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\0android_dlopen_ext\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) g_libdl_symtab[] = {
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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, nullptr, 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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ELFW(SYM_INITIALIZER)(111, &android_dlopen_ext, 1),
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#if defined(__arm__)
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ELFW(SYM_INITIALIZER)(130, &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 g_libdl_symtab starting with index 1, then
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// use g_libdl_chains to find the next index to look at. g_libdl_chains should be set up to
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// walk through every element in g_libdl_symtab, and then end with 0 (sentinel value).
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//
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// That is, g_libdl_chains should look like { 0, 2, 3, ... N, 0 } where N is the number
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// of actual symbols, or nelems(g_libdl_symtab)-1 (since the first element of g_libdl_symtab 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 g_libdl_buckets[1] = { 1 };
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#if defined(__arm__)
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static unsigned g_libdl_chains[] = { 0, 2, 3, 4, 5, 6, 7, 8, 9, 10, 0 };
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#else
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static unsigned g_libdl_chains[] = { 0, 2, 3, 4, 5, 6, 7, 8, 9, 0 };
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#endif
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static soinfo __libdl_info("libdl.so", nullptr, 0, RTLD_GLOBAL);
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// This is used by the dynamic linker. Every process gets these symbols for free.
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soinfo* get_libdl_info() {
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if ((__libdl_info.flags_ & FLAG_LINKED) == 0) {
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__libdl_info.flags_ |= FLAG_LINKED;
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__libdl_info.strtab_ = ANDROID_LIBDL_STRTAB;
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__libdl_info.symtab_ = g_libdl_symtab;
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__libdl_info.nbucket_ = sizeof(g_libdl_buckets)/sizeof(unsigned);
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__libdl_info.nchain_ = sizeof(g_libdl_chains)/sizeof(unsigned);
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__libdl_info.bucket_ = g_libdl_buckets;
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__libdl_info.chain_ = g_libdl_chains;
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__libdl_info.ref_count_ = 1;
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__libdl_info.strtab_size_ = sizeof(ANDROID_LIBDL_STRTAB);
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__libdl_info.local_group_root_ = &__libdl_info;
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}
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return &__libdl_info;
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}
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