lib/libc/dlfcn/dlfcn_elf.c

   1 /*      $NetBSD: dlfcn_elf.c,v 1.13 2012/06/24 15:26:03 christos 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 1.13 2012/06/24 15:26:03 christos 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 dlopen
  42 #undef dlclose
  43 #undef dlsym
  44 #undef dlerror
  45 #undef dladdr
  46 #undef dfinfo
  47
  48 #define dlopen          ___dlopen
  49 #define dlclose         ___dlclose
  50 #define dlsym           ___dlsym
  51 #define dlvsym          ___dlvsym
  52 #define dlerror         ___dlerror
  53 #define dladdr          ___dladdr
  54 #define dlinfo          ___dlinfo
  55 #define dl_iterate_phdr         ___dl_iterate_phdr
  56
  57 #define ELFSIZE ARCH_ELFSIZE
  58 #include "rtld.h"
  59
  60 #ifdef __weak_alias
  61 __weak_alias(dlopen,___dlopen)
  62 __weak_alias(dlclose,___dlclose)
  63 __weak_alias(dlsym,___dlsym)
  64 __weak_alias(dlvsym,___dlvsym)
  65 __weak_alias(dlerror,___dlerror)
  66 __weak_alias(dladdr,___dladdr)
  67 __weak_alias(dlinfo,___dlinfo)
  68 __weak_alias(dl_iterate_phdr,___dl_iterate_phdr)
  69
  70 __weak_alias(__dlopen,___dlopen)
  71 __weak_alias(__dlclose,___dlclose)
  72 __weak_alias(__dlsym,___dlsym)
  73 __weak_alias(__dlvsym,___dlvsym)
  74 __weak_alias(__dlerror,___dlerror)
  75 __weak_alias(__dladdr,___dladdr)
  76 __weak_alias(__dlinfo,___dlinfo)
  77 __weak_alias(__dl_iterate_phdr,___dl_iterate_phdr)
  78 #endif
  79
  80 /*
  81  * For ELF, the dynamic linker directly resolves references to its
  82  * services to functions inside the dynamic linker itself.  These
  83  * weak-symbol stubs are necessary so that "ld" won't complain about
  84  * undefined symbols.  The stubs are executed only when the program is
  85  * linked statically, or when a given service isn't implemented in the
  86  * dynamic linker.  They must return an error if called, and they must
  87  * be weak symbols so that the dynamic linker can override them.
  88  */
  89
  90 static char dlfcn_error[] = "Service unavailable";
  91
  92 /*ARGSUSED*/
  93 void *
  94 dlopen(const char *name, int mode)
  95 {
  96
  97         return NULL;
  98 }
  99
 100 /*ARGSUSED*/
 101 int
 102 dlclose(void *fd)
 103 {
 104
 105         return -1;
 106 }
 107
 108 /*ARGSUSED*/
 109 void *
 110 dlsym(void *handle, const char *name)
 111 {
 112
 113         return NULL;
 114 }
 115
 116 /*ARGSUSED*/
 117 void *
 118 dlvsym(void *handle, const char *name, const char *version)
 119 {
 120
 121         return NULL;
 122 }
 123
 124 /*ARGSUSED*/
 125 __aconst char *
 126 dlerror(void)
 127 {
 128
 129         return dlfcn_error;
 130 }
 131
 132 /*ARGSUSED*/
 133 int
 134 dladdr(const void *addr, Dl_info *dli)
 135 {
 136
 137         return 0;
 138 }
 139
 140 /*ARGSUSED*/
 141 int
 142 dlinfo(void *handle, int req, void *v)
 143 {
 144
 145         return -1;
 146 }
 147
 148 static const char *dlpi_name;
 149 static Elf_Addr dlpi_addr;
 150 static const Elf_Phdr *dlpi_phdr;
 151 static Elf_Half dlpi_phnum;
 152
 153 static void
 154 dl_iterate_phdr_setup(void)
 155 {
 156         const AuxInfo *aux;
 157
 158         _DIAGASSERT(_dlauxinfo() != NULL);
 159
 160         for (aux = _dlauxinfo(); aux->a_type != AT_NULL; ++aux) {
 161                 switch (aux->a_type) {
 162                 case AT_BASE:
 163                         dlpi_addr = aux->a_v;
 164                         break;
 165                 case AT_PHDR:
 166                         dlpi_phdr = (void *)aux->a_v;
 167                         break;
 168                 case AT_PHNUM:
 169                         _DIAGASSERT(__type_fit(Elf_Half, aux->a_v));
 170                         dlpi_phnum = (Elf_Half)aux->a_v;
 171                         break;
 172                 case AT_SUN_EXECNAME:
 173                         dlpi_name = (void *)aux->a_v;
 174                         break;
 175                 }
 176         }
 177 }
 178
 179 /*ARGSUSED*/
 180 int
 181 dl_iterate_phdr(int (*callback)(struct dl_phdr_info *, size_t, void *),
 182     void *data)
 183 {
 184         static bool setup_done;
 185         struct dl_phdr_info phdr_info;
 186
 187         if (!setup_done) {
 188                 /*
 189                  * This can race on the first call to dl_iterate_phdr.
 190                  * dl_iterate_phdr_setup only touches field of pointer size
 191                  * and smaller and such stores are atomic.
 192                  */
 193                 dl_iterate_phdr_setup();
 194 #if !defined(__minix)
 195                 membar_producer();
 196 #endif /* !defined(__minix) */
 197                 setup_done = true;
 198         }
 199
 200         memset(&phdr_info, 0, sizeof(phdr_info));
 201         phdr_info.dlpi_addr = dlpi_addr;
 202         phdr_info.dlpi_phdr = dlpi_phdr;
 203         phdr_info.dlpi_phnum = dlpi_phnum;
 204         phdr_info.dlpi_name = dlpi_name;
 205
 206         return callback(&phdr_info, sizeof(phdr_info), data);
 207 }