resolve.c revision 1.54 
1/*	$OpenBSD: resolve.c,v 1.54 2011/05/22 22:43:47 drahn 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#include "dl_prebind.h"
39
40elf_object_t *_dl_objects;
41elf_object_t *_dl_last_object;
42elf_object_t *_dl_loading_object;
43
44/*
45 * Add a new dynamic object to the object list.
46 */
47void
48_dl_add_object(elf_object_t *object)
49{
50
51	/*
52	 * if this is a new object, prev will be NULL
53	 * != NULL if an object already in the list
54	 * prev == NULL for the first item in the list, but that will
55	 * be the executable.
56	 */
57	if (object->prev != NULL)
58		return;
59
60	if (_dl_objects == NULL) {			/* First object ? */
61		_dl_last_object = _dl_objects = object;
62	} else {
63		_dl_last_object->next = object;
64		object->prev = _dl_last_object;
65		_dl_last_object = object;
66	}
67}
68
69/*
70 * Initialize a new dynamic object.
71 */
72elf_object_t *
73_dl_finalize_object(const char *objname, Elf_Dyn *dynp, Elf_Phdr *phdrp,
74    int phdrc, const int objtype, const long lbase, const long obase)
75{
76	elf_object_t *object;
77#if 0
78	_dl_printf("objname [%s], dynp %p, objtype %x lbase %lx, obase %lx\n",
79	    objname, dynp, objtype, lbase, obase);
80#endif
81	object = _dl_malloc(sizeof(elf_object_t));
82	object->prev = object->next = NULL;
83
84	object->load_dyn = dynp;
85	while (dynp->d_tag != DT_NULL) {
86		if (dynp->d_tag < DT_NUM)
87			object->Dyn.info[dynp->d_tag] = dynp->d_un.d_val;
88		else if (dynp->d_tag >= DT_LOPROC &&
89		    dynp->d_tag < DT_LOPROC + DT_PROCNUM)
90			object->Dyn.info[dynp->d_tag + DT_NUM - DT_LOPROC] =
91			    dynp->d_un.d_val;
92		if (dynp->d_tag == DT_TEXTREL)
93			object->dyn.textrel = 1;
94		if (dynp->d_tag == DT_SYMBOLIC)
95			object->dyn.symbolic = 1;
96		if (dynp->d_tag == DT_BIND_NOW)
97			object->obj_flags = RTLD_NOW;
98		dynp++;
99	}
100
101	/*
102	 *  Now relocate all pointer to dynamic info, but only
103	 *  the ones which have pointer values.
104	 */
105	if (object->Dyn.info[DT_PLTGOT])
106		object->Dyn.info[DT_PLTGOT] += obase;
107	if (object->Dyn.info[DT_HASH])
108		object->Dyn.info[DT_HASH] += obase;
109	if (object->Dyn.info[DT_STRTAB])
110		object->Dyn.info[DT_STRTAB] += obase;
111	if (object->Dyn.info[DT_SYMTAB])
112		object->Dyn.info[DT_SYMTAB] += obase;
113	if (object->Dyn.info[DT_RELA])
114		object->Dyn.info[DT_RELA] += obase;
115	if (object->Dyn.info[DT_SONAME])
116		object->Dyn.info[DT_SONAME] += object->Dyn.info[DT_STRTAB];
117	if (object->Dyn.info[DT_RPATH])
118		object->Dyn.info[DT_RPATH] += object->Dyn.info[DT_STRTAB];
119	if (object->Dyn.info[DT_REL])
120		object->Dyn.info[DT_REL] += obase;
121	if (object->Dyn.info[DT_INIT])
122		object->Dyn.info[DT_INIT] += obase;
123	if (object->Dyn.info[DT_FINI])
124		object->Dyn.info[DT_FINI] += obase;
125	if (object->Dyn.info[DT_JMPREL])
126		object->Dyn.info[DT_JMPREL] += obase;
127
128	if (object->Dyn.info[DT_HASH] != 0) {
129		Elf_Word *hashtab = (Elf_Word *)object->Dyn.info[DT_HASH];
130
131		object->nbuckets = hashtab[0];
132		object->nchains = hashtab[1];
133		object->buckets = hashtab + 2;
134		object->chains = object->buckets + object->nbuckets;
135	}
136
137	object->phdrp = phdrp;
138	object->phdrc = phdrc;
139	object->obj_type = objtype;
140	object->load_base = lbase;
141	object->obj_base = obase;
142	object->load_name = _dl_strdup(objname);
143	if (_dl_loading_object == NULL) {
144		/*
145		 * no loading object, object is the loading object,
146		 * as it is either executable, or dlopened()
147		 */
148		_dl_loading_object = object->load_object = object;
149		DL_DEB(("head %s\n", object->load_name ));
150	} else {
151		object->load_object = _dl_loading_object;
152	}
153	DL_DEB(("obj %s has %s as head\n", object->load_name,
154	    _dl_loading_object->load_name ));
155	object->refcount = 0;
156	TAILQ_INIT(&object->child_list);
157	object->opencount = 0;	/* # dlopen() & exe */
158	object->grprefcount = 0;
159	/* default dev, inode for dlopen-able objects. */
160	object->dev = 0;
161	object->inode = 0;
162	object->lastlookup = 0;
163	TAILQ_INIT(&object->grpsym_list);
164	TAILQ_INIT(&object->grpref_list);
165
166	return(object);
167}
168
169void
170_dl_tailq_free(struct dep_node *n)
171{
172	struct dep_node *next;
173
174	while (n != NULL) {
175		next = TAILQ_NEXT(n, next_sib);
176		_dl_free(n);
177		n = next;
178	}
179}
180
181elf_object_t *free_objects;
182
183void _dl_cleanup_objects(void);
184void
185_dl_cleanup_objects()
186{
187	elf_object_t *nobj, *head;
188	struct dep_node *n, *next;
189
190	n = TAILQ_FIRST(&_dlopened_child_list);
191	while (n != NULL) {
192		next = TAILQ_NEXT(n, next_sib);
193		if (OBJECT_DLREF_CNT(n->data) == 0) {
194			TAILQ_REMOVE(&_dlopened_child_list, n, next_sib);
195			_dl_free(n);
196		}
197		n = next;
198	}
199
200	head = free_objects;
201	free_objects = NULL;
202	while (head != NULL) {
203		if (head->load_name)
204			_dl_free(head->load_name);
205		if (head->sod.sod_name)
206			_dl_free((char *)head->sod.sod_name);
207		_dl_tailq_free(TAILQ_FIRST(&head->grpsym_list));
208		_dl_tailq_free(TAILQ_FIRST(&head->child_list));
209		_dl_tailq_free(TAILQ_FIRST(&head->grpref_list));
210		nobj = head->next;
211		_dl_free(head);
212		head = nobj;
213	}
214}
215
216struct dep_node_head _dlsym_search_list;
217int _dl_search_list_valid = 0;
218
219void
220_dl_rebuild_allobj_grouplist()
221{
222	struct dep_node *n, *m;
223	int global;
224	static int maxgrouplist = 0;
225	static int maxchildlist = 0;
226	int childlistlen = 0, grouplistlen = 0;
227
228	DL_DEB(("rebuil\n"));
229
230	/* get rid of old list */
231	while( (n = TAILQ_FIRST(&_dlsym_search_list)) != NULL) {
232		TAILQ_REMOVE(&_dlsym_search_list, n, next_sib);
233		n->data->obj_global = 0; /* clear the cached global flag */
234		_dl_free(n);
235	}
236
237	/* rebuild list */
238	_dl_newsymsearch();
239	/*
240	 * search dlopened objects: global or req_obj == dlopened_obj
241	 * and and it's children
242	 */
243
244	 _dl_newsymsearch();
245
246	TAILQ_FOREACH(n, &_dlopened_child_list, next_sib) {
247		childlistlen++;
248#if 0
249		DL_DEB(("opened list: %s\n", n->data->load_name));
250#endif
251		global = n->data->obj_flags & RTLD_GLOBAL;
252
253		if (n->data->lastlookup == _dl_searchnum)
254			continue;
255
256		grouplistlen = 0;
257		TAILQ_FOREACH(m, &n->data->grpsym_list, next_sib) {
258			grouplistlen++;
259			if (m->data->lastlookup == _dl_searchnum)
260				continue;
261			if (!global && m->data != n->data) {
262				continue;
263			}
264			m->data->obj_global |= global & RTLD_GLOBAL;
265
266			_dl_append_search(m->data);
267		}
268	}
269	if (grouplistlen > maxgrouplist) {
270		maxgrouplist = grouplistlen ;
271		DL_DEB(("maxgrouplist = %d\n", maxgrouplist));
272	}
273	if (childlistlen > maxchildlist) {
274		maxchildlist = childlistlen;
275		DL_DEB(("maxchildlist = %d\n", maxchildlist));
276	}
277
278#if 0
279	TAILQ_FOREACH(n, &_dlsym_search_list, next_sib) {
280		DL_DEB(("objects: %s global %d\n",
281		    n->data->load_name,
282		    n->data->obj_global));
283	}
284#endif
285
286	_dl_search_list_valid = 1;
287}
288
289void
290_dl_append_search(elf_object_t *object)
291{
292	struct dep_node *n;
293	n = _dl_malloc(sizeof *n);
294	n->data = object;
295
296	object->lastlookup = _dl_searchnum;
297	TAILQ_INSERT_TAIL(&_dlsym_search_list, n, next_sib);
298}
299
300void
301_dl_remove_object(elf_object_t *object)
302{
303	object->prev->next = object->next;
304	if (object->next)
305		object->next->prev = object->prev;
306
307	if (_dl_last_object == object)
308		_dl_last_object = object->prev;
309
310	object->next = free_objects;
311	free_objects = object;
312}
313
314
315int _dl_find_symbol_obj(elf_object_t *object, const char *name,
316    unsigned long hash, int flags, const Elf_Sym **ref,
317    const Elf_Sym **weak_sym,
318    elf_object_t **weak_object);
319
320sym_cache *_dl_symcache;
321int _dl_symcachestat_hits;
322int _dl_symcachestat_lookups;
323
324
325Elf_Addr
326_dl_find_symbol_bysym(elf_object_t *req_obj, unsigned int symidx,
327    const Elf_Sym **this, int flags, const Elf_Sym *ref_sym, const elf_object_t **pobj)
328{
329	Elf_Addr ret;
330	const Elf_Sym *sym;
331	const char *symn;
332	const elf_object_t *sobj;
333
334	_dl_symcachestat_lookups ++;
335	if (_dl_symcache != NULL &&
336	    symidx < req_obj->nchains &&
337	    _dl_symcache[symidx].obj != NULL &&
338	    _dl_symcache[symidx].sym != NULL &&
339	    _dl_symcache[symidx].flags == flags) {
340
341		_dl_symcachestat_hits++;
342		sobj = _dl_symcache[symidx].obj;
343		*this = _dl_symcache[symidx].sym;
344		if (pobj)
345			*pobj = sobj;
346		if (_dl_prebind_validate) /* XXX */
347			prebind_validate(req_obj, symidx, flags, ref_sym);
348		return sobj->obj_base;
349	}
350
351	sym = req_obj->dyn.symtab;
352	sym += symidx;
353	symn = req_obj->dyn.strtab + sym->st_name;
354
355	ret = _dl_find_symbol(symn, this, flags, ref_sym, req_obj, &sobj);
356
357	if (pobj)
358		*pobj = sobj;
359
360	if (_dl_symcache != NULL && symidx < req_obj->nchains) {
361#if 0
362		DL_DEB(("cache miss %d %p %p, %p %p %s %s %d %d %s\n",
363		    symidx,
364		    _dl_symcache[symidx].sym, *this,
365		    _dl_symcache[symidx].obj, sobj, sobj->load_name,
366		    sobj->dyn.strtab + (*this)->st_name,
367		    _dl_symcache[symidx].flags, flags, req_obj->load_name));
368#endif
369
370		_dl_symcache[symidx].sym = *this;
371		_dl_symcache[symidx].obj = sobj;
372		_dl_symcache[symidx].flags = flags;
373	}
374
375	return ret;
376}
377
378int _dl_searchnum = 0;
379void
380_dl_newsymsearch(void)
381{
382	_dl_searchnum += 1;
383
384	if (_dl_searchnum < 0) {
385		/*
386		 * If the signed number rolls over, reset all counters so
387		 * we dont get accidental collision.
388		 */
389		elf_object_t *walkobj;
390		for (walkobj = _dl_objects;
391		    walkobj != NULL;
392		    walkobj = walkobj->next) {
393			walkobj->lastlookup = 0;
394		}
395		_dl_searchnum = 1;
396	}
397}
398
399Elf_Addr
400_dl_find_symbol(const char *name, const Elf_Sym **this,
401    int flags, const Elf_Sym *ref_sym, elf_object_t *req_obj,
402    const elf_object_t **pobj)
403{
404	const Elf_Sym *weak_sym = NULL;
405	unsigned long h = 0;
406	const char *p = name;
407	elf_object_t *object = NULL, *weak_object = NULL;
408	int found = 0;
409	int visit = 0;
410	static int maxvisit = 0;
411	struct dep_node *n, *m;
412
413
414	while (*p) {
415		unsigned long g;
416		h = (h << 4) + *p++;
417		if ((g = h & 0xf0000000))
418			h ^= g >> 24;
419		h &= ~g;
420	}
421
422	if (req_obj->dyn.symbolic)
423		if (_dl_find_symbol_obj(req_obj, name, h, flags, this, &weak_sym,
424		    &weak_object)) {
425			object = req_obj;
426			found = 1;
427			goto found;
428		}
429
430	if (flags & SYM_SEARCH_OBJ) {
431		if (_dl_find_symbol_obj(req_obj, name, h, flags, this,
432		    &weak_sym, &weak_object)) {
433			object = req_obj;
434			found = 1;
435		}
436	} else if (flags & SYM_DLSYM) {
437		if (_dl_find_symbol_obj(req_obj, name, h, flags, this,
438		    &weak_sym, &weak_object)) {
439			object = req_obj;
440			found = 1;
441		}
442		if (weak_object != NULL && found == 0) {
443			object=weak_object;
444			*this = weak_sym;
445			found = 1;
446		}
447		/* search dlopened obj and all children */
448
449		if (found == 0) {
450			TAILQ_FOREACH(n, &req_obj->load_object->grpsym_list,
451			    next_sib) {
452				if (_dl_find_symbol_obj(n->data, name, h,
453				    flags, this,
454				    &weak_sym, &weak_object)) {
455					object = n->data;
456					found = 1;
457					break;
458				}
459			}
460		}
461	} else if ((flags & (SYM_SEARCH_NEXT|SYM_SEARCH_SELF|SYM_SEARCH_OTHER))) {
462		int skip = 0;
463
464		if ((flags & SYM_SEARCH_SELF) || (flags & SYM_SEARCH_NEXT))
465			skip = 1;
466
467		/*
468		 * search dlopened objects: global or req_obj == dlopened_obj
469		 * and and it's children
470		 */
471		TAILQ_FOREACH(n, &_dlopened_child_list, next_sib) {
472			if (((n->data->obj_flags & RTLD_GLOBAL) == 0) &&
473			    (n->data != req_obj->load_object))
474				continue;
475
476			TAILQ_FOREACH(m, &n->data->grpsym_list, next_sib) {
477				if (skip == 1) {
478					if (m->data == req_obj) {
479						skip = 0;
480						if (flags & SYM_SEARCH_NEXT)
481							continue;
482					} else
483						continue;
484				}
485				if ((flags & SYM_SEARCH_OTHER) &&
486				    (m->data == req_obj))
487					continue;
488				if (_dl_find_symbol_obj(m->data, name, h, flags,
489				    this, &weak_sym, &weak_object)) {
490					object = m->data;
491					found = 1;
492					goto found;
493				}
494			}
495		}
496	} else {
497		if (_dl_search_list_valid == 0) {
498			_dl_rebuild_allobj_grouplist();
499		}
500
501		TAILQ_FOREACH(n, &_dlsym_search_list, next_sib) {
502			if (n->data == req_obj->load_object) {
503				TAILQ_FOREACH(m, &n->data->grpsym_list,
504				    next_sib) {
505					visit++;
506					if (_dl_find_symbol_obj(m->data, name,
507					    h, flags, this, &weak_sym,
508					    &weak_object)) {
509						object = m->data;
510						found = 1;
511						goto found;
512					}
513				}
514			}
515			if (((n->data->obj_global & RTLD_GLOBAL) == 0) &&
516			    (n->data != req_obj->load_object))
517				continue;
518
519			//DL_DEB(("searching for %s in %s\n", name, n->data->load_name));
520			visit++;
521			if (_dl_find_symbol_obj(n->data, name, h, flags,
522			    this, &weak_sym, &weak_object)) {
523				object = n->data;
524				found = 1;
525				DL_DEB(("sym %s is in %s\n", name, object->load_name));
526				goto found;
527			}
528		}
529	}
530
531found:
532	if (visit > maxvisit) {
533		maxvisit = visit;
534		DL_DEB(("maxvisit is %d\n", maxvisit));
535	}
536	if (weak_object != NULL && found == 0) {
537		object=weak_object;
538		*this = weak_sym;
539		found = 1;
540	}
541
542
543	if (found == 0) {
544		if ((ref_sym == NULL ||
545		    (ELF_ST_BIND(ref_sym->st_info) != STB_WEAK)) &&
546		    (flags & SYM_WARNNOTFOUND))
547			_dl_printf("%s:%s: undefined symbol '%s'\n",
548			    _dl_progname, req_obj->load_name, name);
549		return (0);
550	}
551
552	if (ref_sym != NULL && ref_sym->st_size != 0 &&
553	    (ref_sym->st_size != (*this)->st_size)  &&
554	    (ELF_ST_TYPE((*this)->st_info) != STT_FUNC) ) {
555		_dl_printf("%s:%s: %s : WARNING: "
556		    "symbol(%s) size mismatch, relink your program\n",
557		    _dl_progname, req_obj->load_name,
558		    object->load_name, name);
559	}
560
561	if (pobj)
562		*pobj = object;
563
564	return (object->obj_base);
565}
566
567int
568_dl_find_symbol_obj(elf_object_t *object, const char *name, unsigned long hash,
569    int flags, const Elf_Sym **this, const Elf_Sym **weak_sym,
570    elf_object_t **weak_object)
571{
572	const Elf_Sym	*symt = object->dyn.symtab;
573	const char	*strt = object->dyn.strtab;
574	long	si;
575	const char *symn;
576
577	for (si = object->buckets[hash % object->nbuckets];
578	    si != STN_UNDEF; si = object->chains[si]) {
579		const Elf_Sym *sym = symt + si;
580
581		if (sym->st_value == 0)
582			continue;
583
584		if (ELF_ST_TYPE(sym->st_info) != STT_NOTYPE &&
585		    ELF_ST_TYPE(sym->st_info) != STT_OBJECT &&
586		    ELF_ST_TYPE(sym->st_info) != STT_FUNC)
587			continue;
588
589		symn = strt + sym->st_name;
590		if (sym != *this && _dl_strcmp(symn, name))
591			continue;
592
593		/* allow this symbol if we are referring to a function
594		 * which has a value, even if section is UNDEF.
595		 * this allows &func to refer to PLT as per the
596		 * ELF spec. st_value is checked above.
597		 * if flags has SYM_PLT set, we must have actual
598		 * symbol, so this symbol is skipped.
599		 */
600		if (sym->st_shndx == SHN_UNDEF) {
601			if ((flags & SYM_PLT) || sym->st_value == 0 ||
602			    ELF_ST_TYPE(sym->st_info) != STT_FUNC)
603				continue;
604		}
605
606		if (ELF_ST_BIND(sym->st_info) == STB_GLOBAL) {
607			*this = sym;
608			return 1;
609		} else if (ELF_ST_BIND(sym->st_info) == STB_WEAK) {
610			if (!*weak_sym) {
611				*weak_sym = sym;
612				*weak_object = object;
613			}
614		}
615	}
616	return 0;
617}
618
619void
620_dl_debug_state(void)
621{
622        /* Debugger stub */
623}
624