resolve.c revision 1.24 
1/*	$OpenBSD: resolve.c,v 1.24 2004/07/05 00:47:40 kjell Exp $ */
2
3/*
4 * Copyright (c) 1998 Per Fogelstrom, Opsycon AB
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 *    notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 *    notice, this list of conditions and the following disclaimer in the
13 *    documentation and/or other materials provided with the distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS
16 * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
17 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
18 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
19 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
20 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
21 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
22 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
23 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
24 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
25 * SUCH DAMAGE.
26 *
27 */
28
29#define _DYN_LOADER
30
31#include <sys/types.h>
32
33#include <nlist.h>
34#include <link.h>
35#include "syscall.h"
36#include "archdep.h"
37#include "resolve.h"
38
39elf_object_t *_dl_objects;
40elf_object_t *_dl_last_object;
41
42/*
43 * Add a new dynamic object to the object list.
44 */
45void
46_dl_add_object(elf_object_t *object)
47{
48
49	/*
50	 * if this is a new object, prev will be NULL
51	 * != NULL if an object already in the list
52	 * prev == NULL for the first item in the list, but that will
53	 * be the executable.
54	 */
55	if (object->prev != NULL)
56		return;
57
58	if (_dl_objects == NULL) {			/* First object ? */
59		_dl_last_object = _dl_objects = object;
60	} else {
61		_dl_last_object->next = object;
62		object->prev = _dl_last_object;
63		_dl_last_object = object;
64	}
65}
66
67/*
68 * Initialize a new dynamic object.
69 */
70elf_object_t *
71_dl_finalize_object(const char *objname, Elf_Dyn *dynp, const u_long *dl_data,
72    const int objtype, const long laddr, const long loff)
73{
74	elf_object_t *object;
75#if 0
76	_dl_printf("objname [%s], dynp %p, dl_data %p, objtype %x laddr %lx, loff %lx\n",
77	    objname, dynp, dl_data, objtype, laddr, loff);
78#endif
79	object = _dl_malloc(sizeof(elf_object_t));
80	object->prev = object->next = NULL;
81
82	object->load_dyn = dynp;
83	while (dynp->d_tag != DT_NULL) {
84		if (dynp->d_tag < DT_NUM)
85			object->Dyn.info[dynp->d_tag] = dynp->d_un.d_val;
86		else if (dynp->d_tag >= DT_LOPROC &&
87		    dynp->d_tag < DT_LOPROC + DT_NUM)
88			object->Dyn.info[dynp->d_tag + DT_NUM - DT_LOPROC] =
89			    dynp->d_un.d_val;
90		if (dynp->d_tag == DT_TEXTREL)
91			object->dyn.textrel = 1;
92		if (dynp->d_tag == DT_SYMBOLIC)
93			object->dyn.symbolic = 1;
94		if (dynp->d_tag == DT_BIND_NOW)
95			object->dyn.bind_now = 1;
96		dynp++;
97	}
98
99	/*
100	 *  Now relocate all pointer to dynamic info, but only
101	 *  the ones which have pointer values.
102	 */
103	if (object->Dyn.info[DT_PLTGOT])
104		object->Dyn.info[DT_PLTGOT] += loff;
105	if (object->Dyn.info[DT_HASH])
106		object->Dyn.info[DT_HASH] += loff;
107	if (object->Dyn.info[DT_STRTAB])
108		object->Dyn.info[DT_STRTAB] += loff;
109	if (object->Dyn.info[DT_SYMTAB])
110		object->Dyn.info[DT_SYMTAB] += loff;
111	if (object->Dyn.info[DT_RELA])
112		object->Dyn.info[DT_RELA] += loff;
113	if (object->Dyn.info[DT_SONAME])
114		object->Dyn.info[DT_SONAME] += loff;
115	if (object->Dyn.info[DT_RPATH])
116		object->Dyn.info[DT_RPATH] += object->Dyn.info[DT_STRTAB];
117	if (object->Dyn.info[DT_REL])
118		object->Dyn.info[DT_REL] += loff;
119	if (object->Dyn.info[DT_INIT])
120		object->Dyn.info[DT_INIT] += loff;
121	if (object->Dyn.info[DT_FINI])
122		object->Dyn.info[DT_FINI] += loff;
123	if (object->Dyn.info[DT_JMPREL])
124		object->Dyn.info[DT_JMPREL] += loff;
125
126	if (object->Dyn.info[DT_HASH] != 0) {
127		Elf_Word *hashtab = (Elf_Word *)object->Dyn.info[DT_HASH];
128
129		object->nbuckets = hashtab[0];
130		object->nchains = hashtab[1];
131		object->buckets = hashtab + 2;
132		object->chains = object->buckets + object->nbuckets;
133	}
134
135	if (dl_data) {
136		object->phdrp = (Elf_Phdr *) dl_data[AUX_phdr];
137		object->phdrc = dl_data[AUX_phnum];
138	}
139	object->obj_type = objtype;
140	object->load_addr = laddr;
141	object->load_offs = loff;
142	object->load_name = _dl_strdup(objname);
143	object->refcount = 1;
144	object->first_child = NULL;
145	object->last_child = NULL;
146	/* default dev, inode for dlopen-able objects. */
147	object->dev = 0;
148	object->inode = 0;
149
150	return(object);
151}
152
153void
154_dl_remove_object(elf_object_t *object)
155{
156	elf_object_t *depobj;
157
158	object->prev->next = object->next;
159	if (object->next)
160		object->next->prev = object->prev;
161
162	if (_dl_last_object == object)
163		_dl_last_object = object->prev;
164
165	if (object->load_name)
166		_dl_free(object->load_name);
167
168	while ((depobj = object->dep_next)) {
169		object->dep_next = object->dep_next->dep_next;
170		_dl_free(depobj);
171	}
172	_dl_free(object);
173}
174
175
176elf_object_t *
177_dl_lookup_object(const char *name)
178{
179	elf_object_t *object;
180
181	object = _dl_objects;
182	while (object) {
183		if (_dl_strcmp(name, object->load_name) == 0)
184			return(object);
185		object = object->next;
186	}
187	return(0);
188}
189
190int find_symbol_obj(elf_object_t *object, const char *name, unsigned long hash,
191    int flags, const Elf_Sym **ref, const Elf_Sym **weak_sym,
192    elf_object_t **weak_object);
193
194sym_cache *_dl_symcache;
195int _dl_symcachestat_hits;
196int _dl_symcachestat_lookups;
197
198Elf_Addr
199_dl_find_symbol_bysym(elf_object_t *req_obj, unsigned int symidx,
200    elf_object_t *startlook, const Elf_Sym **ref, const elf_object_t **pobj,
201    int flags, int req_size)
202{
203	Elf_Addr ret;
204	const Elf_Sym *sym;
205	const char *symn;
206	const elf_object_t *sobj;
207
208	_dl_symcachestat_lookups ++;
209	if ((_dl_symcache != NULL) &&
210	     (symidx < req_obj->nchains) &&
211	     (_dl_symcache[symidx].obj != NULL) &&
212	     (_dl_symcache[symidx].sym != NULL) &&
213	     (_dl_symcache[symidx].flags == flags)) {
214
215		_dl_symcachestat_hits++;
216		sobj = _dl_symcache[symidx].obj;
217		*ref = _dl_symcache[symidx].sym;
218		if (pobj)
219			*pobj = sobj;
220		return sobj->load_offs;
221	}
222
223	sym = req_obj->dyn.symtab;
224	sym += symidx;
225	symn = req_obj->dyn.strtab + sym->st_name;
226
227	ret = _dl_find_symbol(symn, startlook, ref, &sobj,
228	    flags, req_size, req_obj);
229
230	if (pobj)
231		*pobj = sobj;
232
233	if ((_dl_symcache != NULL) &&
234	     (symidx < req_obj->nchains)) {
235		_dl_symcache[symidx].sym = *ref;
236		_dl_symcache[symidx].obj = sobj;
237		_dl_symcache[symidx].flags = flags;
238	}
239
240	return ret;
241}
242
243Elf_Addr
244_dl_find_symbol(const char *name, elf_object_t *startlook,
245    const Elf_Sym **ref, const elf_object_t **pobj,
246    int flags, int req_size, elf_object_t *req_obj)
247{
248	const Elf_Sym *weak_sym = NULL;
249	unsigned long h = 0;
250	const char *p = name;
251	elf_object_t *object, *weak_object = NULL;
252	int found = 0;
253	int lastchance = 0;
254
255	while (*p) {
256		unsigned long g;
257		h = (h << 4) + *p++;
258		if ((g = h & 0xf0000000))
259			h ^= g >> 24;
260		h &= ~g;
261	}
262
263	if (req_obj->dyn.symbolic)
264		if (find_symbol_obj(req_obj, name, h, flags, ref, &weak_sym,
265		    &weak_object)) {
266			object = req_obj;
267			found = 1;
268			goto found;
269		}
270
271retry_nonglobal_dlo:
272	for (object = startlook; object;
273	    object = ((flags & SYM_SEARCH_SELF) ? 0 : object->next)) {
274
275		if ((lastchance == 0) &&
276		    ((object->obj_flags & RTLD_GLOBAL) == 0) &&
277		    (object->obj_type == OBJTYPE_DLO) &&
278		    (object != req_obj))
279			continue;
280
281		if (find_symbol_obj(object, name, h, flags, ref, &weak_sym,
282		    &weak_object)) {
283			found = 1;
284			break;
285		}
286	}
287
288found:
289	if (weak_object != NULL && found == 0) {
290		object=weak_object;
291		*ref = weak_sym;
292		found = 1;
293	}
294
295	if (found == 0) {
296		if (lastchance == 0) {
297			lastchance = 1;
298			goto retry_nonglobal_dlo;
299		}
300		if (flags & SYM_WARNNOTFOUND)
301			_dl_printf("%s:%s: undefined symbol '%s'\n",
302			    _dl_progname, req_obj->load_name, name);
303		return (0);
304	}
305
306	if (req_size != (*ref)->st_size && req_size != 0 &&
307	    (ELF_ST_TYPE((*ref)->st_info) != STT_FUNC)) {
308		_dl_printf("%s:%s: %s : WARNING: "
309		    "symbol(%s) size mismatch, relink your program\n",
310		    _dl_progname, req_obj->load_name,
311		    object->load_name, name);
312	}
313
314	if (pobj)
315		*pobj = object;
316
317	return (object->load_offs);
318}
319
320int
321find_symbol_obj(elf_object_t *object, const char *name, unsigned long hash,
322    int flags, const Elf_Sym **ref, const Elf_Sym **weak_sym,
323    elf_object_t **weak_object)
324{
325	const Elf_Sym	*symt = object->dyn.symtab;
326	const char	*strt = object->dyn.strtab;
327	long	si;
328	const char *symn;
329
330	for (si = object->buckets[hash % object->nbuckets];
331	    si != STN_UNDEF; si = object->chains[si]) {
332		const Elf_Sym *sym = symt + si;
333
334		if (sym->st_value == 0)
335			continue;
336
337		if (ELF_ST_TYPE(sym->st_info) != STT_NOTYPE &&
338		    ELF_ST_TYPE(sym->st_info) != STT_OBJECT &&
339		    ELF_ST_TYPE(sym->st_info) != STT_FUNC)
340			continue;
341
342		symn = strt + sym->st_name;
343		if (sym != *ref && _dl_strcmp(symn, name))
344			continue;
345
346		/* allow this symbol if we are referring to a function
347		 * which has a value, even if section is UNDEF.
348		 * this allows &func to refer to PLT as per the
349		 * ELF spec. st_value is checked above.
350		 * if flags has SYM_PLT set, we must have actual
351		 * symbol, so this symbol is skipped.
352		 */
353		if (sym->st_shndx == SHN_UNDEF) {
354			if ((flags & SYM_PLT) || sym->st_value == 0 ||
355			    ELF_ST_TYPE(sym->st_info) != STT_FUNC)
356				continue;
357		}
358
359		if (ELF_ST_BIND(sym->st_info) == STB_GLOBAL) {
360			*ref = sym;
361			return 1;
362		} else if (ELF_ST_BIND(sym->st_info) == STB_WEAK) {
363			if (!*weak_sym) {
364				*weak_sym = sym;
365				*weak_object = object;
366			}
367		}
368	}
369	return 0;
370}
371