241 lines
7.4 KiB
C++
241 lines
7.4 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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void* tls = const_cast<void*>(__get_tls());
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char** dlerror_slot = &reinterpret_cast<char**>(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* 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());
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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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Elf32_Sym* sym = NULL;
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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 = soinfo_lookup(found, symbol);
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}
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if (sym != NULL) {
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unsigned bind = ELF32_ST_BIND(sym->st_info);
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if (bind == STB_GLOBAL && sym->st_shndx != 0) {
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unsigned ret = sym->st_value + found->load_bias;
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return (void*) ret;
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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 = (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 = soinfo_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 = (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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#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) || defined(ANDROID_MIPS_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
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#error Unsupported architecture. Only ARM, MIPS, and x86 are presently supported.
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#endif
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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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static Elf32_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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ELF32_SYM_INITIALIZER(sizeof(ANDROID_LIBDL_STRTAB) - 1, NULL, 0),
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ELF32_SYM_INITIALIZER( 0, &dlopen, 1),
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ELF32_SYM_INITIALIZER( 7, &dlclose, 1),
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ELF32_SYM_INITIALIZER(15, &dlsym, 1),
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ELF32_SYM_INITIALIZER(21, &dlerror, 1),
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ELF32_SYM_INITIALIZER(29, &dladdr, 1),
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#if defined(ANDROID_ARM_LINKER)
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ELF32_SYM_INITIALIZER(36, &dl_unwind_find_exidx, 1),
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#elif defined(ANDROID_X86_LINKER) || defined(ANDROID_MIPS_LINKER)
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ELF32_SYM_INITIALIZER(36, &dl_iterate_phdr, 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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// A search of the hash table will look through
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// gLibDlSymtab starting with index [1], then
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// use gLibDlChains to find the next index to
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// look at. gLibDlChains should be set up to
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// walk through every element in gLibDlSymtab,
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// and then end with 0 (sentinel value).
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//
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// That is, gLibDlChains 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(gLibDlSymtab)-1
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// (since the first element of gLibDlSymtab is not
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// a real symbol).
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//
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// (see soinfo_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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static unsigned gLibDlBuckets[1] = { 1 };
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static unsigned gLibDlChains[7] = { 0, 2, 3, 4, 5, 6, 0 };
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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, phnum: 0,
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entry: 0, base: 0, size: 0,
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unused: 0, dynamic: 0, unused2: 0, unused3: 0,
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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: 1,
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nchain: 7,
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bucket: gLibDlBuckets,
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chain: gLibDlChains,
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plt_got: 0, plt_rel: 0, plt_rel_count: 0, rel: 0, rel_count: 0,
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preinit_array: 0, preinit_array_count: 0, init_array: 0, init_array_count: 0,
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fini_array: 0, fini_array_count: 0, init_func: 0, fini_func: 0,
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#if defined(ANDROID_ARM_LINKER)
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ARM_exidx: 0, ARM_exidx_count: 0,
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#elif defined(ANDROID_MIPS_LINKER)
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mips_symtabno: 0, mips_local_gotno: 0, mips_gotsym: 0,
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#endif
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refcount: 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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has_text_relocations: false,
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has_DT_SYMBOLIC: true,
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};
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