xref: /freebsd/lib/libc/gen/dlfcn.c (revision 9768746b)
1 /*-
2  * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
3  *
4  * Copyright (c) 1998 John D. Polstra
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 AND CONTRIBUTORS ``AS IS'' AND
17  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
20  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26  * SUCH DAMAGE.
27  */
28 
29 #include <sys/cdefs.h>
30 __FBSDID("$FreeBSD$");
31 
32 #if !defined(IN_LIBDL) || defined(PIC)
33 
34 /*
35  * Linkage to services provided by the dynamic linker.
36  */
37 #include <sys/types.h>
38 #include <sys/mman.h>
39 #include <machine/atomic.h>
40 #include <dlfcn.h>
41 #include <link.h>
42 #include <stddef.h>
43 #include "namespace.h"
44 #include <pthread.h>
45 #include "un-namespace.h"
46 #include "rtld.h"
47 #include "libc_private.h"
48 #include "reentrant.h"
49 
50 static const char sorry[] = "Service unavailable";
51 
52 void _rtld_thread_init(void *);
53 void _rtld_atfork_pre(int *);
54 void _rtld_atfork_post(int *);
55 
56 /*
57  * For ELF, the dynamic linker directly resolves references to its
58  * services to functions inside the dynamic linker itself.  These
59  * weak-symbol stubs are necessary so that "ld" won't complain about
60  * undefined symbols.  The stubs are executed only when the program is
61  * linked statically, or when a given service isn't implemented in the
62  * dynamic linker.  They must return an error if called, and they must
63  * be weak symbols so that the dynamic linker can override them.
64  */
65 
66 #pragma weak _rtld_error
67 void
68 _rtld_error(const char *fmt __unused, ...)
69 {
70 }
71 
72 #pragma weak dladdr
73 int
74 dladdr(const void *addr __unused, Dl_info *dlip __unused)
75 {
76 
77 	_rtld_error(sorry);
78 	return (0);
79 }
80 
81 #pragma weak dlclose
82 int
83 dlclose(void *handle __unused)
84 {
85 
86 	_rtld_error(sorry);
87 	return (-1);
88 }
89 
90 #pragma weak dlerror
91 char *
92 dlerror(void)
93 {
94 
95 	return (__DECONST(char *, sorry));
96 }
97 
98 #pragma weak dllockinit
99 void
100 dllockinit(void *context,
101     void *(*lock_create)(void *context) __unused,
102     void (*rlock_acquire)(void *lock) __unused,
103     void (*wlock_acquire)(void *lock) __unused,
104     void (*lock_release)(void *lock) __unused,
105     void (*lock_destroy)(void *lock) __unused,
106     void (*context_destroy)(void *context) __unused)
107 {
108 
109 	if (context_destroy != NULL)
110 		context_destroy(context);
111 }
112 
113 #pragma weak dlopen
114 void *
115 dlopen(const char *name __unused, int mode __unused)
116 {
117 
118 	_rtld_error(sorry);
119 	return (NULL);
120 }
121 
122 #pragma weak dlsym
123 void *
124 dlsym(void * __restrict handle __unused, const char * __restrict name __unused)
125 {
126 
127 	_rtld_error(sorry);
128 	return (NULL);
129 }
130 
131 #pragma weak dlfunc
132 dlfunc_t
133 dlfunc(void * __restrict handle __unused, const char * __restrict name __unused)
134 {
135 
136 	_rtld_error(sorry);
137 	return (NULL);
138 }
139 
140 #pragma weak dlvsym
141 void *
142 dlvsym(void * __restrict handle __unused, const char * __restrict name __unused,
143     const char * __restrict version __unused)
144 {
145 
146 	_rtld_error(sorry);
147 	return (NULL);
148 }
149 
150 #pragma weak dlinfo
151 int
152 dlinfo(void * __restrict handle __unused, int request __unused,
153     void * __restrict p __unused)
154 {
155 
156 	_rtld_error(sorry);
157 	return (0);
158 }
159 
160 #pragma weak _rtld_thread_init
161 void
162 _rtld_thread_init(void *li __unused)
163 {
164 
165 	_rtld_error(sorry);
166 }
167 
168 #ifndef IN_LIBDL
169 static pthread_once_t dl_phdr_info_once = PTHREAD_ONCE_INIT;
170 static struct dl_phdr_info phdr_info;
171 static mutex_t dl_phdr_info_lock = MUTEX_INITIALIZER;
172 
173 static void
174 dl_init_phdr_info(void)
175 {
176 	Elf_Auxinfo *auxp;
177 	unsigned int i;
178 
179 	for (auxp = __elf_aux_vector; auxp->a_type != AT_NULL; auxp++) {
180 		switch (auxp->a_type) {
181 		case AT_BASE:
182 			phdr_info.dlpi_addr = (Elf_Addr)auxp->a_un.a_ptr;
183 			break;
184 		case AT_EXECPATH:
185 			phdr_info.dlpi_name = (const char *)auxp->a_un.a_ptr;
186 			break;
187 		case AT_PHDR:
188 			phdr_info.dlpi_phdr =
189 			    (const Elf_Phdr *)auxp->a_un.a_ptr;
190 			break;
191 		case AT_PHNUM:
192 			phdr_info.dlpi_phnum = (Elf_Half)auxp->a_un.a_val;
193 			break;
194 		}
195 	}
196 	for (i = 0; i < phdr_info.dlpi_phnum; i++) {
197 		if (phdr_info.dlpi_phdr[i].p_type == PT_TLS) {
198 			phdr_info.dlpi_tls_modid = 1;
199 		}
200 	}
201 	phdr_info.dlpi_adds = 1;
202 }
203 #endif
204 
205 #pragma weak dl_iterate_phdr
206 int
207 dl_iterate_phdr(int (*callback)(struct dl_phdr_info *, size_t, void *) __unused,
208     void *data __unused)
209 {
210 #ifndef IN_LIBDL
211 	tls_index ti;
212 	int ret;
213 
214 	__init_elf_aux_vector();
215 	if (__elf_aux_vector == NULL)
216 		return (1);
217 	_once(&dl_phdr_info_once, dl_init_phdr_info);
218 	ti.ti_module = 1;
219 	ti.ti_offset = 0;
220 	mutex_lock(&dl_phdr_info_lock);
221 	phdr_info.dlpi_tls_data = __tls_get_addr(&ti);
222 	ret = callback(&phdr_info, sizeof(phdr_info), data);
223 	mutex_unlock(&dl_phdr_info_lock);
224 	return (ret);
225 #else
226 	return (0);
227 #endif
228 }
229 
230 #pragma weak fdlopen
231 void *
232 fdlopen(int fd __unused, int mode __unused)
233 {
234 
235 	_rtld_error(sorry);
236 	return (NULL);
237 }
238 
239 #pragma weak _rtld_atfork_pre
240 void
241 _rtld_atfork_pre(int *locks __unused)
242 {
243 }
244 
245 #pragma weak _rtld_atfork_post
246 void
247 _rtld_atfork_post(int *locks __unused)
248 {
249 }
250 
251 #pragma weak _rtld_addr_phdr
252 int
253 _rtld_addr_phdr(const void *addr __unused,
254     struct dl_phdr_info *phdr_info_a __unused)
255 {
256 
257 	return (0);
258 }
259 
260 #pragma weak _rtld_get_stack_prot
261 int
262 _rtld_get_stack_prot(void)
263 {
264 #ifndef IN_LIBDL
265 	unsigned i;
266 	int r;
267 	static int ret;
268 
269 	r = atomic_load_int(&ret);
270 	if (r != 0)
271 		return (r);
272 
273 	_once(&dl_phdr_info_once, dl_init_phdr_info);
274 	r = PROT_EXEC | PROT_READ | PROT_WRITE;
275 	for (i = 0; i < phdr_info.dlpi_phnum; i++) {
276 		if (phdr_info.dlpi_phdr[i].p_type != PT_GNU_STACK)
277 			continue;
278 		r = PROT_READ | PROT_WRITE;
279 		if ((phdr_info.dlpi_phdr[i].p_flags & PF_X) != 0)
280 			r |= PROT_EXEC;
281 		break;
282 	}
283 	atomic_store_int(&ret, r);
284 	return (r);
285 #else
286 	return (0);
287 #endif
288 }
289 
290 #pragma weak _rtld_is_dlopened
291 int
292 _rtld_is_dlopened(void *arg __unused)
293 {
294 
295 	return (0);
296 }
297 
298 #endif /* !defined(IN_LIBDL) || defined(PIC) */
299