1 /*- 2 * Copyright (c) 1998 John D. Polstra 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 17 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 24 * SUCH DAMAGE. 25 * 26 * $FreeBSD$ 27 */ 28 29 /* 30 * Linkage to services provided by the dynamic linker. These are 31 * implemented differently in ELF and a.out, because the dynamic 32 * linkers have different interfaces. 33 */ 34 35 #ifdef __ELF__ 36 37 #include <dlfcn.h> 38 #include <stddef.h> 39 40 static const char sorry[] = "Service unavailable"; 41 42 /* 43 * For ELF, the dynamic linker directly resolves references to its 44 * services to functions inside the dynamic linker itself. These 45 * weak-symbol stubs are necessary so that "ld" won't complain about 46 * undefined symbols. The stubs are executed only when the program is 47 * linked statically, or when a given service isn't implemented in the 48 * dynamic linker. They must return an error if called, and they must 49 * be weak symbols so that the dynamic linker can override them. 50 */ 51 52 #pragma weak _rtld_error 53 void 54 _rtld_error(const char *fmt, ...) 55 { 56 } 57 58 #pragma weak dladdr 59 int 60 dladdr(const void *addr, Dl_info *dlip) 61 { 62 _rtld_error(sorry); 63 return 0; 64 } 65 66 #pragma weak dlclose 67 int 68 dlclose(void *handle) 69 { 70 _rtld_error(sorry); 71 return -1; 72 } 73 74 #pragma weak dlerror 75 const char * 76 dlerror(void) 77 { 78 return sorry; 79 } 80 81 #pragma weak dllockinit 82 void 83 dllockinit(void *context, 84 void *(*lock_create)(void *context), 85 void (*rlock_acquire)(void *lock), 86 void (*wlock_acquire)(void *lock), 87 void (*lock_release)(void *lock), 88 void (*lock_destroy)(void *lock), 89 void (*context_destroy)(void *context)) 90 { 91 if (context_destroy != NULL) 92 context_destroy(context); 93 } 94 95 #pragma weak dlopen 96 void * 97 dlopen(const char *name, int mode) 98 { 99 _rtld_error(sorry); 100 return NULL; 101 } 102 103 #pragma weak dlsym 104 void * 105 dlsym(void *handle, const char *name) 106 { 107 _rtld_error(sorry); 108 return NULL; 109 } 110 111 #else /* a.out format */ 112 113 #include <sys/types.h> 114 #include <nlist.h> /* XXX - Required by link.h */ 115 #include <dlfcn.h> 116 #include <link.h> 117 #include <stddef.h> 118 119 /* 120 * For a.out, entry to the dynamic linker is via these trampolines. 121 * They enter the dynamic linker through the ld_entry struct that was 122 * passed back from the dynamic linker at startup time. 123 */ 124 125 /* GCC is needed because we use its __builtin_return_address construct. */ 126 127 #ifndef __GNUC__ 128 #error "GCC is needed to compile this file" 129 #endif 130 131 /* 132 * These variables are set by code in crt0.o. For compatibility with 133 * old executables, they must be common, not extern. 134 */ 135 struct ld_entry *__ldso_entry; /* Entry points to dynamic linker */ 136 int __ldso_version; /* Dynamic linker version number */ 137 138 int 139 dladdr(const void *addr, Dl_info *dlip) 140 { 141 if (__ldso_entry == NULL || __ldso_version < LDSO_VERSION_HAS_DLADDR) 142 return 0; 143 return (__ldso_entry->dladdr)(addr, dlip); 144 } 145 146 int 147 dlclose(void *handle) 148 { 149 if (__ldso_entry == NULL) 150 return -1; 151 return (__ldso_entry->dlclose)(handle); 152 } 153 154 const char * 155 dlerror(void) 156 { 157 if (__ldso_entry == NULL) 158 return "Service unavailable"; 159 return (__ldso_entry->dlerror)(); 160 } 161 162 void * 163 dlopen(const char *name, int mode) 164 { 165 if (__ldso_entry == NULL) 166 return NULL; 167 return (__ldso_entry->dlopen)(name, mode); 168 } 169 170 void * 171 dlsym(void *handle, const char *name) 172 { 173 if (__ldso_entry == NULL) 174 return NULL; 175 if (__ldso_version >= LDSO_VERSION_HAS_DLSYM3) { 176 void *retaddr = __builtin_return_address(0); /* __GNUC__ only */ 177 return (__ldso_entry->dlsym3)(handle, name, retaddr); 178 } else 179 return (__ldso_entry->dlsym)(handle, name); 180 } 181 182 #endif /* __ELF__ */ 183