1 /* $NetBSD: dlfcn_elf.c,v 1.9 2011/03/12 21:55:09 joerg Exp $ */ 2 3 /* 4 * Copyright (c) 2000 Takuya SHIOZAKI 5 * All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 17 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 18 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 19 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 21 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 22 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 23 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 24 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 25 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 26 */ 27 28 #include <sys/cdefs.h> 29 #if defined(LIBC_SCCS) && !defined(lint) 30 __RCSID("$NetBSD: dlfcn_elf.c,v 1.9 2011/03/12 21:55:09 joerg Exp $"); 31 #endif /* LIBC_SCCS and not lint */ 32 33 #include "namespace.h" 34 #include <sys/atomic.h> 35 #include <elf.h> 36 #include <errno.h> 37 #include <string.h> 38 #include <stdbool.h> 39 40 #undef dlopen 41 #undef dlclose 42 #undef dlsym 43 #undef dlerror 44 #undef dladdr 45 #undef dfinfo 46 47 #define dlopen ___dlopen 48 #define dlclose ___dlclose 49 #define dlsym ___dlsym 50 #define dlerror ___dlerror 51 #define dladdr ___dladdr 52 #define dlinfo ___dlinfo 53 #define dl_iterate_phdr ___dl_iterate_phdr 54 55 #define ELFSIZE ARCH_ELFSIZE 56 #include "rtld.h" 57 58 #ifdef __weak_alias 59 __weak_alias(dlopen,___dlopen) 60 __weak_alias(dlclose,___dlclose) 61 __weak_alias(dlsym,___dlsym) 62 __weak_alias(dlerror,___dlerror) 63 __weak_alias(dladdr,___dladdr) 64 __weak_alias(dlinfo,___dlinfo) 65 __weak_alias(dl_iterate_phdr,___dl_iterate_phdr) 66 67 __weak_alias(__dlopen,___dlopen) 68 __weak_alias(__dlclose,___dlclose) 69 __weak_alias(__dlsym,___dlsym) 70 __weak_alias(__dlerror,___dlerror) 71 __weak_alias(__dladdr,___dladdr) 72 __weak_alias(__dlinfo,___dlinfo) 73 __weak_alias(__dl_iterate_phdr,___dl_iterate_phdr) 74 #endif 75 76 /* 77 * For ELF, the dynamic linker directly resolves references to its 78 * services to functions inside the dynamic linker itself. These 79 * weak-symbol stubs are necessary so that "ld" won't complain about 80 * undefined symbols. The stubs are executed only when the program is 81 * linked statically, or when a given service isn't implemented in the 82 * dynamic linker. They must return an error if called, and they must 83 * be weak symbols so that the dynamic linker can override them. 84 */ 85 86 static char dlfcn_error[] = "Service unavailable"; 87 88 /*ARGSUSED*/ 89 void * 90 dlopen(const char *name, int mode) 91 { 92 93 return NULL; 94 } 95 96 /*ARGSUSED*/ 97 int 98 dlclose(void *fd) 99 { 100 101 return -1; 102 } 103 104 /*ARGSUSED*/ 105 void * 106 dlsym(void *handle, const char *name) 107 { 108 109 return NULL; 110 } 111 112 /*ARGSUSED*/ 113 __aconst char * 114 dlerror() 115 { 116 117 return dlfcn_error; 118 } 119 120 /*ARGSUSED*/ 121 int 122 dladdr(const void *addr, Dl_info *dli) 123 { 124 125 return 0; 126 } 127 128 /*ARGSUSED*/ 129 int 130 dlinfo(void *handle, int req, void *v) 131 { 132 133 return -1; 134 } 135 136 static const char *dlpi_name; 137 static Elf_Addr dlpi_addr; 138 static const Elf_Phdr *dlpi_phdr; 139 static Elf_Half dlpi_phnum; 140 141 /* 142 * Declare as common symbol to allow new libc with older binaries to 143 * not trigger an undefined reference. 144 */ 145 extern __dso_hidden void *__auxinfo; 146 147 static void 148 dl_iterate_phdr_setup(void) 149 { 150 const AuxInfo *aux; 151 152 if (__auxinfo == NULL) 153 return; 154 155 for (aux = __auxinfo; aux->a_type != AT_NULL; ++aux) { 156 switch (aux->a_type) { 157 case AT_BASE: 158 dlpi_addr = aux->a_v; 159 break; 160 case AT_PHDR: 161 dlpi_phdr = (void *)aux->a_v; 162 break; 163 case AT_PHNUM: 164 dlpi_phnum = aux->a_v; 165 break; 166 case AT_SUN_EXECNAME: 167 dlpi_name = (void *)aux->a_v; 168 break; 169 } 170 } 171 } 172 173 /*ARGSUSED*/ 174 int 175 dl_iterate_phdr(int (*callback)(struct dl_phdr_info *, size_t, void *), 176 void *data) 177 { 178 static bool setup_done; 179 struct dl_phdr_info phdr_info; 180 181 if (__auxinfo == NULL) 182 return EOPNOTSUPP; 183 184 if (!setup_done) { 185 /* 186 * This can race on the first call to dl_iterate_phdr. 187 * dl_iterate_phdr_setup only touches field of pointer size 188 * and smaller and such stores are atomic. 189 */ 190 dl_iterate_phdr_setup(); 191 membar_producer(); 192 setup_done = true; 193 } 194 195 memset(&phdr_info, 0, sizeof(phdr_info)); 196 phdr_info.dlpi_addr = dlpi_addr; 197 phdr_info.dlpi_phdr = dlpi_phdr; 198 phdr_info.dlpi_phnum = dlpi_phnum; 199 phdr_info.dlpi_name = dlpi_name; 200 201 return callback(&phdr_info, sizeof(phdr_info), data); 202 } 203