1 /* $NetBSD: dlfcn_elf.c,v 1.17 2023/07/04 19:24:25 riastradh 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 1.17 2023/07/04 19:24:25 riastradh 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 dl_iterate_phdr
42 #undef dlopen
43 #undef dlclose
44 #undef dlsym
45 #undef dlerror
46 #undef dladdr
47 #undef dfinfo
48
49 #define dlopen ___dlopen
50 #define dlclose ___dlclose
51 #define dlsym ___dlsym
52 #define dlvsym ___dlvsym
53 #define dlerror ___dlerror
54 #define dladdr ___dladdr
55 #define dlinfo ___dlinfo
56 #define dl_iterate_phdr ___dl_iterate_phdr
57
58 #define ELFSIZE ARCH_ELFSIZE
59 #include "rtld.h"
60
61 #ifdef __weak_alias
62 __weak_alias(dlopen,___dlopen)
63 __weak_alias(dlclose,___dlclose)
64 __weak_alias(dlsym,___dlsym)
65 __weak_alias(dlvsym,___dlvsym)
66 __weak_alias(dlerror,___dlerror)
67 __weak_alias(dladdr,___dladdr)
68 __weak_alias(dlinfo,___dlinfo)
69 __weak_alias(dl_iterate_phdr,___dl_iterate_phdr)
70
71 __weak_alias(__dlopen,___dlopen)
72 __weak_alias(__dlclose,___dlclose)
73 __weak_alias(__dlsym,___dlsym)
74 __weak_alias(__dlvsym,___dlvsym)
75 __weak_alias(__dlerror,___dlerror)
76 __weak_alias(__dladdr,___dladdr)
77 __weak_alias(__dlinfo,___dlinfo)
78 __weak_alias(__dl_iterate_phdr,___dl_iterate_phdr)
79 __weak_alias(__dl_cxa_refcount, ___dl_cxa_refcount)
80 #endif
81
82 /*
83 * For ELF, the dynamic linker directly resolves references to its
84 * services to functions inside the dynamic linker itself. These
85 * weak-symbol stubs are necessary so that "ld" won't complain about
86 * undefined symbols. The stubs are executed only when the program is
87 * linked statically, or when a given service isn't implemented in the
88 * dynamic linker. They must return an error if called, and they must
89 * be weak symbols so that the dynamic linker can override them.
90 */
91
92 static char dlfcn_error[] = "Service unavailable";
93
94 /*ARGSUSED*/
95 void *
dlopen(const char * name,int mode)96 dlopen(const char *name, int mode)
97 {
98
99 return NULL;
100 }
101
102 /*ARGSUSED*/
103 int
dlclose(void * fd)104 dlclose(void *fd)
105 {
106
107 return -1;
108 }
109
110 /*ARGSUSED*/
111 void *
dlsym(void * handle,const char * name)112 dlsym(void *handle, const char *name)
113 {
114
115 return NULL;
116 }
117
118 /*ARGSUSED*/
119 void *
dlvsym(void * handle,const char * name,const char * version)120 dlvsym(void *handle, const char *name, const char *version)
121 {
122
123 return NULL;
124 }
125
126 /*ARGSUSED*/
127 __aconst char *
dlerror(void)128 dlerror(void)
129 {
130
131 return dlfcn_error;
132 }
133
134 /*ARGSUSED*/
135 int
dladdr(const void * addr,Dl_info * dli)136 dladdr(const void *addr, Dl_info *dli)
137 {
138
139 return 0;
140 }
141
142 /*ARGSUSED*/
143 int
dlinfo(void * handle,int req,void * v)144 dlinfo(void *handle, int req, void *v)
145 {
146
147 return -1;
148 }
149
150 static const char *dlpi_name;
151 static Elf_Addr dlpi_addr;
152 static const Elf_Phdr *dlpi_phdr;
153 static Elf_Half dlpi_phnum;
154
155 static void
dl_iterate_phdr_setup(void)156 dl_iterate_phdr_setup(void)
157 {
158 const AuxInfo *aux;
159
160 _DIAGASSERT(_dlauxinfo() != NULL);
161
162 for (aux = _dlauxinfo(); aux->a_type != AT_NULL; ++aux) {
163 switch (aux->a_type) {
164 case AT_BASE:
165 dlpi_addr = aux->a_v;
166 break;
167 case AT_PHDR:
168 dlpi_phdr = (void *)aux->a_v;
169 break;
170 case AT_PHNUM:
171 _DIAGASSERT(__type_fit(Elf_Half, aux->a_v));
172 dlpi_phnum = (Elf_Half)aux->a_v;
173 break;
174 case AT_SUN_EXECNAME:
175 dlpi_name = (void *)aux->a_v;
176 break;
177 }
178 }
179
180 if (!dlpi_phdr)
181 return;
182
183 const Elf_Phdr *phdr = (const Elf_Phdr *)dlpi_phdr;
184 const Elf_Phdr *phlimit = phdr + dlpi_phnum;
185
186 for (; phdr < phlimit; ++phdr) {
187 if (phdr->p_type == PT_PHDR)
188 dlpi_addr = (uintptr_t)phdr - phdr->p_vaddr;
189 }
190 }
191
192 /*ARGSUSED*/
193 int
dl_iterate_phdr(int (* callback)(struct dl_phdr_info *,size_t,void *),void * data)194 dl_iterate_phdr(int (*callback)(struct dl_phdr_info *, size_t, void *),
195 void *data)
196 {
197 static bool setup_done;
198 struct dl_phdr_info phdr_info;
199
200 if (!setup_done) {
201 /*
202 * This can race on the first call to dl_iterate_phdr.
203 * dl_iterate_phdr_setup only touches field of pointer size
204 * and smaller and such stores are atomic.
205 */
206 dl_iterate_phdr_setup();
207 membar_producer();
208 setup_done = true;
209 }
210 membar_consumer();
211
212 memset(&phdr_info, 0, sizeof(phdr_info));
213 phdr_info.dlpi_addr = dlpi_addr;
214 phdr_info.dlpi_phdr = dlpi_phdr;
215 phdr_info.dlpi_phnum = dlpi_phnum;
216 phdr_info.dlpi_name = dlpi_name;
217
218 return callback(&phdr_info, sizeof(phdr_info), data);
219 }
220
221 void ___dl_cxa_refcount(void *, ssize_t);
222
223 /*ARGSUSED*/
224 void
___dl_cxa_refcount(void * dso_symbol,ssize_t delta)225 ___dl_cxa_refcount(void *dso_symbol, ssize_t delta)
226 {
227 }
228