resolve.c revision 1.23 
1/*	$OpenBSD: resolve.c,v 1.23 2004/05/25 18:07:20 mickey 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
80	object = _dl_malloc(sizeof(elf_object_t));
81	object->prev = object->next = NULL;
82
83	object->load_dyn = dynp;
84	while (dynp->d_tag != DT_NULL) {
85		if (dynp->d_tag < DT_NUM)
86			object->Dyn.info[dynp->d_tag] = dynp->d_un.d_val;
87		else if (dynp->d_tag >= DT_LOPROC &&
88		    dynp->d_tag < DT_LOPROC + DT_NUM)
89			object->Dyn.info[dynp->d_tag + DT_NUM - DT_LOPROC] =
90			    dynp->d_un.d_val;
91		if (dynp->d_tag == DT_TEXTREL)
92			object->dyn.textrel = 1;
93		if (dynp->d_tag == DT_SYMBOLIC)
94			object->dyn.symbolic = 1;
95		if (dynp->d_tag == DT_BIND_NOW)
96			object->dyn.bind_now = 1;
97		dynp++;
98	}
99
100	/*
101	 *  Now relocate all pointer to dynamic info, but only
102	 *  the ones which have pointer values.
103	 */
104	if (object->Dyn.info[DT_PLTGOT])
105		object->Dyn.info[DT_PLTGOT] += loff;
106	if (object->Dyn.info[DT_HASH])
107		object->Dyn.info[DT_HASH] += loff;
108	if (object->Dyn.info[DT_STRTAB])
109		object->Dyn.info[DT_STRTAB] += loff;
110	if (object->Dyn.info[DT_SYMTAB])
111		object->Dyn.info[DT_SYMTAB] += loff;
112	if (object->Dyn.info[DT_RELA])
113		object->Dyn.info[DT_RELA] += loff;
114	if (object->Dyn.info[DT_SONAME])
115		object->Dyn.info[DT_SONAME] += loff;
116	if (object->Dyn.info[DT_RPATH])
117		object->Dyn.info[DT_RPATH] += object->Dyn.info[DT_STRTAB];
118	if (object->Dyn.info[DT_REL])
119		object->Dyn.info[DT_REL] += loff;
120	if (object->Dyn.info[DT_INIT])
121		object->Dyn.info[DT_INIT] += loff;
122	if (object->Dyn.info[DT_FINI])
123		object->Dyn.info[DT_FINI] += loff;
124	if (object->Dyn.info[DT_JMPREL])
125		object->Dyn.info[DT_JMPREL] += loff;
126
127	if (object->Dyn.info[DT_HASH] != 0) {
128		Elf_Word *hashtab = (Elf_Word *)object->Dyn.info[DT_HASH];
129
130		object->nbuckets = hashtab[0];
131		object->nchains = hashtab[1];
132		object->buckets = hashtab + 2;
133		object->chains = object->buckets + object->nbuckets;
134	}
135
136	if (dl_data) {
137		object->phdrp = (Elf_Phdr *) dl_data[AUX_phdr];
138		object->phdrc = dl_data[AUX_phnum];
139	}
140	object->obj_type = objtype;
141	object->load_addr = laddr;
142	object->load_offs = loff;
143	object->load_name = _dl_strdup(objname);
144	object->refcount = 1;
145	object->first_child = NULL;
146	object->last_child = NULL;
147	return(object);
148}
149
150void
151_dl_remove_object(elf_object_t *object)
152{
153	elf_object_t *depobj;
154
155	object->prev->next = object->next;
156	if (object->next)
157		object->next->prev = object->prev;
158
159	if (_dl_last_object == object)
160		_dl_last_object = object->prev;
161
162	if (object->load_name)
163		_dl_free(object->load_name);
164
165	while ((depobj = object->dep_next)) {
166		object->dep_next = object->dep_next->dep_next;
167		_dl_free(depobj);
168	}
169	_dl_free(object);
170}
171
172
173elf_object_t *
174_dl_lookup_object(const char *name)
175{
176	elf_object_t *object;
177
178	object = _dl_objects;
179	while (object) {
180		if (_dl_strcmp(name, object->load_name) == 0)
181			return(object);
182		object = object->next;
183	}
184	return(0);
185}
186
187int find_symbol_obj(elf_object_t *object, const char *name, unsigned long hash,
188    int flags, const Elf_Sym **ref, const Elf_Sym **weak_sym,
189    elf_object_t **weak_object);
190
191sym_cache *_dl_symcache;
192int _dl_symcachestat_hits;
193int _dl_symcachestat_lookups;
194
195Elf_Addr
196_dl_find_symbol_bysym(elf_object_t *req_obj, unsigned int symidx,
197    elf_object_t *startlook, const Elf_Sym **ref, const elf_object_t **pobj,
198    int flags, int req_size)
199{
200	Elf_Addr ret;
201	const Elf_Sym *sym;
202	const char *symn;
203	const elf_object_t *sobj;
204
205	_dl_symcachestat_lookups ++;
206	if ((_dl_symcache != NULL) &&
207	     (symidx < req_obj->nchains) &&
208	     (_dl_symcache[symidx].obj != NULL) &&
209	     (_dl_symcache[symidx].sym != NULL) &&
210	     (_dl_symcache[symidx].flags == flags)) {
211
212		_dl_symcachestat_hits++;
213		sobj = _dl_symcache[symidx].obj;
214		*ref = _dl_symcache[symidx].sym;
215		if (pobj)
216			*pobj = sobj;
217		return sobj->load_offs;
218	}
219
220	sym = req_obj->dyn.symtab;
221	sym += symidx;
222	symn = req_obj->dyn.strtab + sym->st_name;
223
224	ret = _dl_find_symbol(symn, startlook, ref, &sobj,
225	    flags, req_size, req_obj);
226
227	if (pobj)
228		*pobj = sobj;
229
230	if ((_dl_symcache != NULL) &&
231	     (symidx < req_obj->nchains)) {
232		_dl_symcache[symidx].sym = *ref;
233		_dl_symcache[symidx].obj = sobj;
234		_dl_symcache[symidx].flags = flags;
235	}
236
237	return ret;
238}
239
240Elf_Addr
241_dl_find_symbol(const char *name, elf_object_t *startlook,
242    const Elf_Sym **ref, const elf_object_t **pobj,
243    int flags, int req_size, elf_object_t *req_obj)
244{
245	const Elf_Sym *weak_sym = NULL;
246	unsigned long h = 0;
247	const char *p = name;
248	elf_object_t *object, *weak_object = NULL;
249	int found = 0;
250	int lastchance = 0;
251
252	while (*p) {
253		unsigned long g;
254		h = (h << 4) + *p++;
255		if ((g = h & 0xf0000000))
256			h ^= g >> 24;
257		h &= ~g;
258	}
259
260	if (req_obj->dyn.symbolic)
261		if (find_symbol_obj(req_obj, name, h, flags, ref, &weak_sym,
262		    &weak_object)) {
263			object = req_obj;
264			found = 1;
265			goto found;
266		}
267
268retry_nonglobal_dlo:
269	for (object = startlook; object;
270	    object = ((flags & SYM_SEARCH_SELF) ? 0 : object->next)) {
271
272		if ((lastchance == 0) &&
273		    ((object->obj_flags & RTLD_GLOBAL) == 0) &&
274		    (object->obj_type == OBJTYPE_DLO) &&
275		    (object != req_obj))
276			continue;
277
278		if (find_symbol_obj(object, name, h, flags, ref, &weak_sym,
279		    &weak_object)) {
280			found = 1;
281			break;
282		}
283	}
284
285found:
286	if (weak_object != NULL && found == 0) {
287		object=weak_object;
288		*ref = weak_sym;
289		found = 1;
290	}
291
292	if (found == 0) {
293		if (lastchance == 0) {
294			lastchance = 1;
295			goto retry_nonglobal_dlo;
296		}
297		if (flags & SYM_WARNNOTFOUND)
298			_dl_printf("%s:%s: undefined symbol '%s'\n",
299			    _dl_progname, req_obj->load_name, name);
300		return (0);
301	}
302
303	if (req_size != (*ref)->st_size && req_size != 0 &&
304	    (ELF_ST_TYPE((*ref)->st_info) != STT_FUNC)) {
305		_dl_printf("%s:%s: %s : WARNING: "
306		    "symbol(%s) size mismatch, relink your program\n",
307		    _dl_progname, req_obj->load_name,
308		    object->load_name, name);
309	}
310
311	if (pobj)
312		*pobj = object;
313
314	return (object->load_offs);
315}
316
317int
318find_symbol_obj(elf_object_t *object, const char *name, unsigned long hash,
319    int flags, const Elf_Sym **ref, const Elf_Sym **weak_sym,
320    elf_object_t **weak_object)
321{
322	const Elf_Sym	*symt = object->dyn.symtab;
323	const char	*strt = object->dyn.strtab;
324	long	si;
325	const char *symn;
326
327	for (si = object->buckets[hash % object->nbuckets];
328	    si != STN_UNDEF; si = object->chains[si]) {
329		const Elf_Sym *sym = symt + si;
330
331		if (sym->st_value == 0)
332			continue;
333
334		if (ELF_ST_TYPE(sym->st_info) != STT_NOTYPE &&
335		    ELF_ST_TYPE(sym->st_info) != STT_OBJECT &&
336		    ELF_ST_TYPE(sym->st_info) != STT_FUNC)
337			continue;
338
339		symn = strt + sym->st_name;
340		if (sym != *ref && _dl_strcmp(symn, name))
341			continue;
342
343		/* allow this symbol if we are referring to a function
344		 * which has a value, even if section is UNDEF.
345		 * this allows &func to refer to PLT as per the
346		 * ELF spec. st_value is checked above.
347		 * if flags has SYM_PLT set, we must have actual
348		 * symbol, so this symbol is skipped.
349		 */
350		if (sym->st_shndx == SHN_UNDEF) {
351			if ((flags & SYM_PLT) || sym->st_value == 0 ||
352			    ELF_ST_TYPE(sym->st_info) != STT_FUNC)
353				continue;
354		}
355
356		if (ELF_ST_BIND(sym->st_info) == STB_GLOBAL) {
357			*ref = sym;
358			return 1;
359		} else if (ELF_ST_BIND(sym->st_info) == STB_WEAK) {
360			if (!*weak_sym) {
361				*weak_sym = sym;
362				*weak_object = object;
363			}
364		}
365	}
366	return 0;
367}
368