| /* |
| * Copyright (C) 2007 The Android Open Source Project |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| #include <dlfcn.h> |
| #include <pthread.h> |
| #include <stdio.h> |
| |
| #include <private/ScopedPthreadMutexLocker.h> |
| |
| #include "linker.h" |
| #include "linker_format.h" |
| |
| /* This file hijacks the symbols stubbed out in libdl.so. */ |
| |
| static char dl_err_buf[1024]; |
| static const char* dl_err_str; |
| |
| #define likely(expr) __builtin_expect (expr, 1) |
| #define unlikely(expr) __builtin_expect (expr, 0) |
| |
| pthread_mutex_t dl_lock = PTHREAD_RECURSIVE_MUTEX_INITIALIZER; |
| |
| static void set_dlerror(const char* msg, const char* detail) { |
| if (detail != NULL) { |
| format_buffer(dl_err_buf, sizeof(dl_err_buf), "%s: %s", msg, detail); |
| } else { |
| format_buffer(dl_err_buf, sizeof(dl_err_buf), "%s", msg); |
| } |
| dl_err_str = (const char*) &dl_err_buf[0]; |
| } |
| |
| void *dlopen(const char* filename, int flag) { |
| ScopedPthreadMutexLocker locker(&dl_lock); |
| soinfo* result = find_library(filename); |
| if (result == NULL) { |
| set_dlerror("dlopen failed", linker_get_error()); |
| return NULL; |
| } |
| soinfo_call_constructors(result); |
| result->refcount++; |
| return result; |
| } |
| |
| const char* dlerror() { |
| const char* old_value = dl_err_str; |
| dl_err_str = NULL; |
| return (const char*) old_value; |
| } |
| |
| void* dlsym(void* handle, const char* symbol) { |
| ScopedPthreadMutexLocker locker(&dl_lock); |
| |
| if (unlikely(handle == 0)) { |
| set_dlerror("dlsym library handle is null", NULL); |
| return NULL; |
| } |
| if (unlikely(symbol == 0)) { |
| set_dlerror("dlsym symbol name is null", NULL); |
| return NULL; |
| } |
| |
| soinfo* found = NULL; |
| Elf32_Sym* sym = NULL; |
| if (handle == RTLD_DEFAULT) { |
| sym = lookup(symbol, &found, NULL); |
| } else if (handle == RTLD_NEXT) { |
| void* ret_addr = __builtin_return_address(0); |
| soinfo* si = find_containing_library(ret_addr); |
| |
| sym = NULL; |
| if (si && si->next) { |
| sym = lookup(symbol, &found, si->next); |
| } |
| } else { |
| found = (soinfo*) handle; |
| sym = soinfo_lookup(found, symbol); |
| } |
| |
| if (likely(sym != 0)) { |
| unsigned bind = ELF32_ST_BIND(sym->st_info); |
| |
| if (likely((bind == STB_GLOBAL) && (sym->st_shndx != 0))) { |
| unsigned ret = sym->st_value + found->load_bias; |
| return (void*) ret; |
| } |
| |
| set_dlerror("symbol found but not global", symbol); |
| return NULL; |
| } else { |
| set_dlerror("undefined symbol", symbol); |
| return NULL; |
| } |
| } |
| |
| int dladdr(const void* addr, Dl_info* info) { |
| ScopedPthreadMutexLocker locker(&dl_lock); |
| |
| // Determine if this address can be found in any library currently mapped. |
| soinfo* si = find_containing_library(addr); |
| if (si == NULL) { |
| return 0; |
| } |
| |
| memset(info, 0, sizeof(Dl_info)); |
| |
| info->dli_fname = si->name; |
| // Address at which the shared object is loaded. |
| info->dli_fbase = (void*) si->base; |
| |
| // Determine if any symbol in the library contains the specified address. |
| Elf32_Sym *sym = soinfo_find_symbol(si, addr); |
| if (sym != NULL) { |
| info->dli_sname = si->strtab + sym->st_name; |
| info->dli_saddr = (void*)(si->load_bias + sym->st_value); |
| } |
| |
| return 1; |
| } |
| |
| int dlclose(void* handle) { |
| ScopedPthreadMutexLocker locker(&dl_lock); |
| return soinfo_unload((soinfo*) handle); |
| } |
| |
| #if defined(ANDROID_ARM_LINKER) |
| // 0000000 00011111 111112 22222222 2333333 333344444444445555555 |
| // 0123456 78901234 567890 12345678 9012345 678901234567890123456 |
| #define ANDROID_LIBDL_STRTAB \ |
| "dlopen\0dlclose\0dlsym\0dlerror\0dladdr\0dl_unwind_find_exidx\0" |
| |
| #elif defined(ANDROID_X86_LINKER) || defined(ANDROID_MIPS_LINKER) |
| // 0000000 00011111 111112 22222222 2333333 3333444444444455 |
| // 0123456 78901234 567890 12345678 9012345 6789012345678901 |
| #define ANDROID_LIBDL_STRTAB \ |
| "dlopen\0dlclose\0dlsym\0dlerror\0dladdr\0dl_iterate_phdr\0" |
| #else |
| #error Unsupported architecture. Only ARM, MIPS, and x86 are presently supported. |
| #endif |
| |
| // name_offset: starting index of the name in libdl_info.strtab |
| #define ELF32_SYM_INITIALIZER(name_offset, value, shndx) \ |
| { name_offset, \ |
| reinterpret_cast<Elf32_Addr>(reinterpret_cast<void*>(value)), \ |
| /* st_size */ 0, \ |
| (shndx == 0) ? 0 : (STB_GLOBAL << 4), \ |
| /* st_other */ 0, \ |
| shndx } |
| |
| static Elf32_Sym libdl_symtab[] = { |
| // Total length of libdl_info.strtab, including trailing 0. |
| // This is actually the STH_UNDEF entry. Technically, it's |
| // supposed to have st_name == 0, but instead, it points to an index |
| // in the strtab with a \0 to make iterating through the symtab easier. |
| ELF32_SYM_INITIALIZER(sizeof(ANDROID_LIBDL_STRTAB) - 1, NULL, 0), |
| ELF32_SYM_INITIALIZER( 0, &dlopen, 1), |
| ELF32_SYM_INITIALIZER( 7, &dlclose, 1), |
| ELF32_SYM_INITIALIZER(15, &dlsym, 1), |
| ELF32_SYM_INITIALIZER(21, &dlerror, 1), |
| ELF32_SYM_INITIALIZER(29, &dladdr, 1), |
| #if defined(ANDROID_ARM_LINKER) |
| ELF32_SYM_INITIALIZER(36, &dl_unwind_find_exidx, 1), |
| #elif defined(ANDROID_X86_LINKER) || defined(ANDROID_MIPS_LINKER) |
| ELF32_SYM_INITIALIZER(36, &dl_iterate_phdr, 1), |
| #endif |
| }; |
| |
| /* Fake out a hash table with a single bucket. |
| * A search of the hash table will look through |
| * libdl_symtab starting with index [1], then |
| * use libdl_chains to find the next index to |
| * look at. libdl_chains should be set up to |
| * walk through every element in libdl_symtab, |
| * and then end with 0 (sentinel value). |
| * |
| * I.e., libdl_chains should look like |
| * { 0, 2, 3, ... N, 0 } where N is the number |
| * of actual symbols, or nelems(libdl_symtab)-1 |
| * (since the first element of libdl_symtab is not |
| * a real symbol). |
| * |
| * (see _elf_lookup()) |
| * |
| * Note that adding any new symbols here requires |
| * stubbing them out in libdl. |
| */ |
| static unsigned libdl_buckets[1] = { 1 }; |
| static unsigned libdl_chains[7] = { 0, 2, 3, 4, 5, 6, 0 }; |
| |
| soinfo libdl_info = { |
| name: "libdl.so", |
| |
| phdr: 0, phnum: 0, |
| entry: 0, base: 0, size: 0, |
| unused: 0, dynamic: 0, unused2: 0, unused3: 0, |
| next: 0, |
| |
| flags: FLAG_LINKED, |
| |
| strtab: ANDROID_LIBDL_STRTAB, |
| symtab: libdl_symtab, |
| |
| nbucket: 1, |
| nchain: 7, |
| bucket: libdl_buckets, |
| chain: libdl_chains, |
| |
| plt_got: 0, plt_rel: 0, plt_rel_count: 0, rel: 0, rel_count: 0, |
| preinit_array: 0, preinit_array_count: 0, init_array: 0, init_array_count: 0, |
| fini_array: 0, fini_array_count: 0, init_func: 0, fini_func: 0, |
| |
| #if defined(ANDROID_ARM_LINKER) |
| ARM_exidx: 0, ARM_exidx_count: 0, |
| #elif defined(ANDROID_MIPS_LINKER) |
| mips_symtabno: 0, mips_local_gotno: 0, mips_gotsym: 0, |
| #endif |
| |
| refcount: 0, |
| { l_addr: 0, l_name: 0, l_ld: 0, l_next: 0, l_prev: 0, }, |
| constructors_called: 0, load_bias: 0, has_text_relocations: 0, |
| }; |