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
92static char dlfcn_error[] = "Service unavailable";
93
94/*ARGSUSED*/
95void *
96dlopen(const char *name, int mode)
97{
98
99	return NULL;
100}
101
102/*ARGSUSED*/
103int
104dlclose(void *fd)
105{
106
107	return -1;
108}
109
110/*ARGSUSED*/
111void *
112dlsym(void *handle, const char *name)
113{
114
115	return NULL;
116}
117
118/*ARGSUSED*/
119void *
120dlvsym(void *handle, const char *name, const char *version)
121{
122
123	return NULL;
124}
125
126/*ARGSUSED*/
127__aconst char *
128dlerror(void)
129{
130
131	return dlfcn_error;
132}
133
134/*ARGSUSED*/
135int
136dladdr(const void *addr, Dl_info *dli)
137{
138
139	return 0;
140}
141
142/*ARGSUSED*/
143int
144dlinfo(void *handle, int req, void *v)
145{
146
147	return -1;
148}
149
150static const char *dlpi_name;
151static Elf_Addr dlpi_addr;
152static const Elf_Phdr *dlpi_phdr;
153static Elf_Half dlpi_phnum;
154
155static void
156dl_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*/
193int
194dl_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
221void ___dl_cxa_refcount(void *, ssize_t);
222
223/*ARGSUSED*/
224void
225___dl_cxa_refcount(void *dso_symbol, ssize_t delta)
226{
227}
228