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dlfcn_elf.c revision 1.9 
      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