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dlfcn_elf.c revision 1.13 
      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 		membar_producer();
    195 		setup_done = true;
    196 	}
    197 
    198 	memset(&phdr_info, 0, sizeof(phdr_info));
    199 	phdr_info.dlpi_addr = dlpi_addr;
    200 	phdr_info.dlpi_phdr = dlpi_phdr;
    201 	phdr_info.dlpi_phnum = dlpi_phnum;
    202 	phdr_info.dlpi_name = dlpi_name;
    203 
    204 	return callback(&phdr_info, sizeof(phdr_info), data);
    205 }
    206