resolve.c revision 1.22 
1/*	$OpenBSD: resolve.c,v 1.22 2004/05/25 15:56:18 deraadt 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, int flags, int req_size)
198{
199	Elf_Addr ret;
200	const Elf_Sym *sym;
201	const char *symn;
202
203	_dl_symcachestat_lookups ++;
204	if ((_dl_symcache != NULL) &&
205	     (symidx < req_obj->nchains) &&
206	     (_dl_symcache[symidx].sym != NULL) &&
207	     (_dl_symcache[symidx].flags == flags)) {
208
209		_dl_symcachestat_hits++;
210		*ref = _dl_symcache[symidx].sym;
211		return _dl_symcache[symidx].offset;
212	}
213
214	sym = req_obj->dyn.symtab;
215	sym += symidx;
216	symn = req_obj->dyn.strtab + sym->st_name;
217
218	ret = _dl_find_symbol(symn, startlook, ref, flags, req_size, req_obj);
219
220	if ((_dl_symcache != NULL) &&
221	     (symidx < req_obj->nchains)) {
222		_dl_symcache[symidx].sym = *ref;
223		_dl_symcache[symidx].offset = ret;
224		_dl_symcache[symidx].flags = flags;
225	}
226
227	return ret;
228}
229
230Elf_Addr
231_dl_find_symbol(const char *name, elf_object_t *startlook,
232    const Elf_Sym **ref, int flags, int req_size, elf_object_t *req_obj)
233{
234	const Elf_Sym *weak_sym = NULL;
235	unsigned long h = 0;
236	const char *p = name;
237	elf_object_t *object, *weak_object = NULL;
238	int found = 0;
239	int lastchance = 0;
240
241	while (*p) {
242		unsigned long g;
243		h = (h << 4) + *p++;
244		if ((g = h & 0xf0000000))
245			h ^= g >> 24;
246		h &= ~g;
247	}
248
249	if (req_obj->dyn.symbolic)
250		if (find_symbol_obj(req_obj, name, h, flags, ref, &weak_sym,
251		    &weak_object)) {
252			object = req_obj;
253			found = 1;
254			goto found;
255		}
256
257retry_nonglobal_dlo:
258	for (object = startlook; object;
259	    object = ((flags & SYM_SEARCH_SELF) ? 0 : object->next)) {
260
261		if ((lastchance == 0) &&
262		    ((object->obj_flags & RTLD_GLOBAL) == 0) &&
263		    (object->obj_type == OBJTYPE_DLO) &&
264		    (object != req_obj))
265			continue;
266
267		if (find_symbol_obj(object, name, h, flags, ref, &weak_sym,
268		    &weak_object)) {
269			found = 1;
270			break;
271		}
272	}
273
274found:
275	if (weak_object != NULL && found == 0) {
276		object=weak_object;
277		*ref = weak_sym;
278		found = 1;
279	}
280
281	if (found == 0) {
282		if (lastchance == 0) {
283			lastchance = 1;
284			goto retry_nonglobal_dlo;
285		}
286		if (flags & SYM_WARNNOTFOUND)
287			_dl_printf("%s:%s: undefined symbol '%s'\n",
288			    _dl_progname, req_obj->load_name, name);
289		return (0);
290	}
291
292	if (req_size != (*ref)->st_size && req_size != 0 &&
293	    (ELF_ST_TYPE((*ref)->st_info) != STT_FUNC)) {
294		_dl_printf("%s:%s: %s : WARNING: "
295		    "symbol(%s) size mismatch, relink your program\n",
296		    _dl_progname, req_obj->load_name,
297		    object->load_name, name);
298	}
299
300	return (object->load_offs);
301}
302
303int
304find_symbol_obj(elf_object_t *object, const char *name, unsigned long hash,
305    int flags, const Elf_Sym **ref, const Elf_Sym **weak_sym,
306    elf_object_t **weak_object)
307{
308	const Elf_Sym	*symt = object->dyn.symtab;
309	const char	*strt = object->dyn.strtab;
310	long	si;
311	const char *symn;
312
313	for (si = object->buckets[hash % object->nbuckets];
314	    si != STN_UNDEF; si = object->chains[si]) {
315		const Elf_Sym *sym = symt + si;
316
317		if (sym->st_value == 0)
318			continue;
319
320		if (ELF_ST_TYPE(sym->st_info) != STT_NOTYPE &&
321		    ELF_ST_TYPE(sym->st_info) != STT_OBJECT &&
322		    ELF_ST_TYPE(sym->st_info) != STT_FUNC)
323			continue;
324
325		symn = strt + sym->st_name;
326		if (sym != *ref && _dl_strcmp(symn, name))
327			continue;
328
329		/* allow this symbol if we are referring to a function
330		 * which has a value, even if section is UNDEF.
331		 * this allows &func to refer to PLT as per the
332		 * ELF spec. st_value is checked above.
333		 * if flags has SYM_PLT set, we must have actual
334		 * symbol, so this symbol is skipped.
335		 */
336		if (sym->st_shndx == SHN_UNDEF) {
337			if ((flags & SYM_PLT) || sym->st_value == 0 ||
338			    ELF_ST_TYPE(sym->st_info) != STT_FUNC)
339				continue;
340		}
341
342		if (ELF_ST_BIND(sym->st_info) == STB_GLOBAL) {
343			*ref = sym;
344			return 1;
345		} else if (ELF_ST_BIND(sym->st_info) == STB_WEAK) {
346			if (!*weak_sym) {
347				*weak_sym = sym;
348				*weak_object = object;
349			}
350		}
351	}
352	return 0;
353}
354