1 /* $NetBSD: dlfcn_elf.c,v 1.17 2023/07/04 19:24:25 riastradh 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 1.17 2023/07/04 19:24:25 riastradh Exp $"); 31 #endif /* LIBC_SCCS and not lint */ 32 33 #include "namespace.h" 34 #include <sys/atomic.h> 35 #include <assert.h> 36 #include <elf.h> 37 #include <errno.h> 38 #include <string.h> 39 #include <stdbool.h> 40 41 #undef dl_iterate_phdr 42 #undef dlopen 43 #undef dlclose 44 #undef dlsym 45 #undef dlerror 46 #undef dladdr 47 #undef dfinfo 48 49 #define dlopen ___dlopen 50 #define dlclose ___dlclose 51 #define dlsym ___dlsym 52 #define dlvsym ___dlvsym 53 #define dlerror ___dlerror 54 #define dladdr ___dladdr 55 #define dlinfo ___dlinfo 56 #define dl_iterate_phdr ___dl_iterate_phdr 57 58 #define ELFSIZE ARCH_ELFSIZE 59 #include "rtld.h" 60 61 #ifdef __weak_alias 62 __weak_alias(dlopen,___dlopen) 63 __weak_alias(dlclose,___dlclose) 64 __weak_alias(dlsym,___dlsym) 65 __weak_alias(dlvsym,___dlvsym) 66 __weak_alias(dlerror,___dlerror) 67 __weak_alias(dladdr,___dladdr) 68 __weak_alias(dlinfo,___dlinfo) 69 __weak_alias(dl_iterate_phdr,___dl_iterate_phdr) 70 71 __weak_alias(__dlopen,___dlopen) 72 __weak_alias(__dlclose,___dlclose) 73 __weak_alias(__dlsym,___dlsym) 74 __weak_alias(__dlvsym,___dlvsym) 75 __weak_alias(__dlerror,___dlerror) 76 __weak_alias(__dladdr,___dladdr) 77 __weak_alias(__dlinfo,___dlinfo) 78 __weak_alias(__dl_iterate_phdr,___dl_iterate_phdr) 79 __weak_alias(__dl_cxa_refcount, ___dl_cxa_refcount) 80 #endif 81 82 /* 83 * For ELF, the dynamic linker directly resolves references to its 84 * services to functions inside the dynamic linker itself. These 85 * weak-symbol stubs are necessary so that "ld" won't complain about 86 * undefined symbols. The stubs are executed only when the program is 87 * linked statically, or when a given service isn't implemented in the 88 * dynamic linker. They must return an error if called, and they must 89 * be weak symbols so that the dynamic linker can override them. 90 */ 91 92 static char dlfcn_error[] = "Service unavailable"; 93 94 /*ARGSUSED*/ 95 void * 96 dlopen(const char *name, int mode) 97 { 98 99 return NULL; 100 } 101 102 /*ARGSUSED*/ 103 int 104 dlclose(void *fd) 105 { 106 107 return -1; 108 } 109 110 /*ARGSUSED*/ 111 void * 112 dlsym(void *handle, const char *name) 113 { 114 115 return NULL; 116 } 117 118 /*ARGSUSED*/ 119 void * 120 dlvsym(void *handle, const char *name, const char *version) 121 { 122 123 return NULL; 124 } 125 126 /*ARGSUSED*/ 127 __aconst char * 128 dlerror(void) 129 { 130 131 return dlfcn_error; 132 } 133 134 /*ARGSUSED*/ 135 int 136 dladdr(const void *addr, Dl_info *dli) 137 { 138 139 return 0; 140 } 141 142 /*ARGSUSED*/ 143 int 144 dlinfo(void *handle, int req, void *v) 145 { 146 147 return -1; 148 } 149 150 static const char *dlpi_name; 151 static Elf_Addr dlpi_addr; 152 static const Elf_Phdr *dlpi_phdr; 153 static Elf_Half dlpi_phnum; 154 155 static void 156 dl_iterate_phdr_setup(void) 157 { 158 const AuxInfo *aux; 159 160 _DIAGASSERT(_dlauxinfo() != NULL); 161 162 for (aux = _dlauxinfo(); aux->a_type != AT_NULL; ++aux) { 163 switch (aux->a_type) { 164 case AT_BASE: 165 dlpi_addr = aux->a_v; 166 break; 167 case AT_PHDR: 168 dlpi_phdr = (void *)aux->a_v; 169 break; 170 case AT_PHNUM: 171 _DIAGASSERT(__type_fit(Elf_Half, aux->a_v)); 172 dlpi_phnum = (Elf_Half)aux->a_v; 173 break; 174 case AT_SUN_EXECNAME: 175 dlpi_name = (void *)aux->a_v; 176 break; 177 } 178 } 179 180 if (!dlpi_phdr) 181 return; 182 183 const Elf_Phdr *phdr = (const Elf_Phdr *)dlpi_phdr; 184 const Elf_Phdr *phlimit = phdr + dlpi_phnum; 185 186 for (; phdr < phlimit; ++phdr) { 187 if (phdr->p_type == PT_PHDR) 188 dlpi_addr = (uintptr_t)phdr - phdr->p_vaddr; 189 } 190 } 191 192 /*ARGSUSED*/ 193 int 194 dl_iterate_phdr(int (*callback)(struct dl_phdr_info *, size_t, void *), 195 void *data) 196 { 197 static bool setup_done; 198 struct dl_phdr_info phdr_info; 199 200 if (!setup_done) { 201 /* 202 * This can race on the first call to dl_iterate_phdr. 203 * dl_iterate_phdr_setup only touches field of pointer size 204 * and smaller and such stores are atomic. 205 */ 206 dl_iterate_phdr_setup(); 207 membar_producer(); 208 setup_done = true; 209 } 210 membar_consumer(); 211 212 memset(&phdr_info, 0, sizeof(phdr_info)); 213 phdr_info.dlpi_addr = dlpi_addr; 214 phdr_info.dlpi_phdr = dlpi_phdr; 215 phdr_info.dlpi_phnum = dlpi_phnum; 216 phdr_info.dlpi_name = dlpi_name; 217 218 return callback(&phdr_info, sizeof(phdr_info), data); 219 } 220 221 void ___dl_cxa_refcount(void *, ssize_t); 222 223 /*ARGSUSED*/ 224 void 225 ___dl_cxa_refcount(void *dso_symbol, ssize_t delta) 226 { 227 } 228
Indexes created Mon Sep 22 21:09:42 GMT 2025