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dlfcn_elf.c revision 1.11 
      1 /*	$NetBSD: dlfcn_elf.c,v 1.11 2012/02/16 23:00:39 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 1.11 2012/02/16 23:00:39 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	dlvsym		___dlvsym
     51 #define	dlerror		___dlerror
     52 #define	dladdr		___dladdr
     53 #define	dlinfo		___dlinfo
     54 #define	dl_iterate_phdr		___dl_iterate_phdr
     55 
     56 #define ELFSIZE ARCH_ELFSIZE
     57 #include "rtld.h"
     58 
     59 #ifdef __weak_alias
     60 __weak_alias(dlopen,___dlopen)
     61 __weak_alias(dlclose,___dlclose)
     62 __weak_alias(dlsym,___dlsym)
     63 __weak_alias(dlvsym,___dlvsym)
     64 __weak_alias(dlerror,___dlerror)
     65 __weak_alias(dladdr,___dladdr)
     66 __weak_alias(dlinfo,___dlinfo)
     67 __weak_alias(dl_iterate_phdr,___dl_iterate_phdr)
     68 
     69 __weak_alias(__dlopen,___dlopen)
     70 __weak_alias(__dlclose,___dlclose)
     71 __weak_alias(__dlsym,___dlsym)
     72 __weak_alias(__dlvsym,___dlvsym)
     73 __weak_alias(__dlerror,___dlerror)
     74 __weak_alias(__dladdr,___dladdr)
     75 __weak_alias(__dlinfo,___dlinfo)
     76 __weak_alias(__dl_iterate_phdr,___dl_iterate_phdr)
     77 #endif
     78 
     79 /*
     80  * For ELF, the dynamic linker directly resolves references to its
     81  * services to functions inside the dynamic linker itself.  These
     82  * weak-symbol stubs are necessary so that "ld" won't complain about
     83  * undefined symbols.  The stubs are executed only when the program is
     84  * linked statically, or when a given service isn't implemented in the
     85  * dynamic linker.  They must return an error if called, and they must
     86  * be weak symbols so that the dynamic linker can override them.
     87  */
     88 
     89 static char dlfcn_error[] = "Service unavailable";
     90 
     91 /*ARGSUSED*/
     92 void *
     93 dlopen(const char *name, int mode)
     94 {
     95 
     96 	return NULL;
     97 }
     98 
     99 /*ARGSUSED*/
    100 int
    101 dlclose(void *fd)
    102 {
    103 
    104 	return -1;
    105 }
    106 
    107 /*ARGSUSED*/
    108 void *
    109 dlsym(void *handle, const char *name)
    110 {
    111 
    112 	return NULL;
    113 }
    114 
    115 /*ARGSUSED*/
    116 void *
    117 dlvsym(void *handle, const char *name, const char *version)
    118 {
    119 
    120 	return NULL;
    121 }
    122 
    123 /*ARGSUSED*/
    124 __aconst char *
    125 dlerror()
    126 {
    127 
    128 	return dlfcn_error;
    129 }
    130 
    131 /*ARGSUSED*/
    132 int
    133 dladdr(const void *addr, Dl_info *dli)
    134 {
    135 
    136 	return 0;
    137 }
    138 
    139 /*ARGSUSED*/
    140 int
    141 dlinfo(void *handle, int req, void *v)
    142 {
    143 
    144 	return -1;
    145 }
    146 
    147 static const char *dlpi_name;
    148 static Elf_Addr dlpi_addr;
    149 static const Elf_Phdr *dlpi_phdr;
    150 static Elf_Half dlpi_phnum;
    151 
    152 static void
    153 dl_iterate_phdr_setup(void)
    154 {
    155 	const AuxInfo *aux;
    156 
    157 	_DIAGASSERT(_dlauxinfo() != NULL);
    158 
    159 	for (aux = _dlauxinfo(); aux->a_type != AT_NULL; ++aux) {
    160 		switch (aux->a_type) {
    161 		case AT_BASE:
    162 			dlpi_addr = aux->a_v;
    163 			break;
    164 		case AT_PHDR:
    165 			dlpi_phdr = (void *)aux->a_v;
    166 			break;
    167 		case AT_PHNUM:
    168 			dlpi_phnum = aux->a_v;
    169 			break;
    170 		case AT_SUN_EXECNAME:
    171 			dlpi_name = (void *)aux->a_v;
    172 			break;
    173 		}
    174 	}
    175 }
    176 
    177 /*ARGSUSED*/
    178 int
    179 dl_iterate_phdr(int (*callback)(struct dl_phdr_info *, size_t, void *),
    180     void *data)
    181 {
    182 	static bool setup_done;
    183 	struct dl_phdr_info phdr_info;
    184 
    185 	if (!setup_done) {
    186 		/*
    187 		 * This can race on the first call to dl_iterate_phdr.
    188 		 * dl_iterate_phdr_setup only touches field of pointer size
    189 		 * and smaller and such stores are atomic.
    190 		 */
    191 		dl_iterate_phdr_setup();
    192 		membar_producer();
    193 		setup_done = true;
    194 	}
    195 
    196 	memset(&phdr_info, 0, sizeof(phdr_info));
    197 	phdr_info.dlpi_addr = dlpi_addr;
    198 	phdr_info.dlpi_phdr = dlpi_phdr;
    199 	phdr_info.dlpi_phnum = dlpi_phnum;
    200 	phdr_info.dlpi_name = dlpi_name;
    201 
    202 	return callback(&phdr_info, sizeof(phdr_info), data);
    203 }
    204