resolve.c revision 1.55 
1/*	$OpenBSD: resolve.c,v 1.55 2011/05/26 05:10:49 otto 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	/*
241	 * search dlopened objects: global or req_obj == dlopened_obj
242	 * and and it's children
243	 */
244	TAILQ_FOREACH(n, &_dlopened_child_list, next_sib) {
245		childlistlen++;
246#if 0
247		DL_DEB(("opened list: %s\n", n->data->load_name));
248#endif
249		global = n->data->obj_flags & RTLD_GLOBAL;
250
251		if (n->data->lastlookup == _dl_searchnum)
252			continue;
253
254		grouplistlen = 0;
255		TAILQ_FOREACH(m, &n->data->grpsym_list, next_sib) {
256			grouplistlen++;
257			if (m->data->lastlookup == _dl_searchnum)
258				continue;
259			if (!global && m->data != n->data) {
260				continue;
261			}
262			m->data->obj_global |= global & RTLD_GLOBAL;
263
264			_dl_append_search(m->data);
265		}
266	}
267	if (grouplistlen > maxgrouplist) {
268		maxgrouplist = grouplistlen ;
269		DL_DEB(("maxgrouplist = %d\n", maxgrouplist));
270	}
271	if (childlistlen > maxchildlist) {
272		maxchildlist = childlistlen;
273		DL_DEB(("maxchildlist = %d\n", maxchildlist));
274	}
275
276#if 0
277	TAILQ_FOREACH(n, &_dlsym_search_list, next_sib) {
278		DL_DEB(("objects: %s global %d\n",
279		    n->data->load_name,
280		    n->data->obj_global));
281	}
282#endif
283
284	_dl_search_list_valid = 1;
285}
286
287void
288_dl_append_search(elf_object_t *object)
289{
290	struct dep_node *n;
291	n = _dl_malloc(sizeof *n);
292	n->data = object;
293
294	object->lastlookup = _dl_searchnum;
295	TAILQ_INSERT_TAIL(&_dlsym_search_list, n, next_sib);
296}
297
298void
299_dl_remove_object(elf_object_t *object)
300{
301	object->prev->next = object->next;
302	if (object->next)
303		object->next->prev = object->prev;
304
305	if (_dl_last_object == object)
306		_dl_last_object = object->prev;
307
308	object->next = free_objects;
309	free_objects = object;
310}
311
312
313int _dl_find_symbol_obj(elf_object_t *object, const char *name,
314    unsigned long hash, int flags, const Elf_Sym **ref,
315    const Elf_Sym **weak_sym,
316    elf_object_t **weak_object);
317
318sym_cache *_dl_symcache;
319int _dl_symcachestat_hits;
320int _dl_symcachestat_lookups;
321
322
323Elf_Addr
324_dl_find_symbol_bysym(elf_object_t *req_obj, unsigned int symidx,
325    const Elf_Sym **this, int flags, const Elf_Sym *ref_sym, const elf_object_t **pobj)
326{
327	Elf_Addr ret;
328	const Elf_Sym *sym;
329	const char *symn;
330	const elf_object_t *sobj;
331
332	_dl_symcachestat_lookups ++;
333	if (_dl_symcache != NULL &&
334	    symidx < req_obj->nchains &&
335	    _dl_symcache[symidx].obj != NULL &&
336	    _dl_symcache[symidx].sym != NULL &&
337	    _dl_symcache[symidx].flags == flags) {
338
339		_dl_symcachestat_hits++;
340		sobj = _dl_symcache[symidx].obj;
341		*this = _dl_symcache[symidx].sym;
342		if (pobj)
343			*pobj = sobj;
344		if (_dl_prebind_validate) /* XXX */
345			prebind_validate(req_obj, symidx, flags, ref_sym);
346		return sobj->obj_base;
347	}
348
349	sym = req_obj->dyn.symtab;
350	sym += symidx;
351	symn = req_obj->dyn.strtab + sym->st_name;
352
353	ret = _dl_find_symbol(symn, this, flags, ref_sym, req_obj, &sobj);
354
355	if (pobj)
356		*pobj = sobj;
357
358	if (_dl_symcache != NULL && symidx < req_obj->nchains) {
359#if 0
360		DL_DEB(("cache miss %d %p %p, %p %p %s %s %d %d %s\n",
361		    symidx,
362		    _dl_symcache[symidx].sym, *this,
363		    _dl_symcache[symidx].obj, sobj, sobj->load_name,
364		    sobj->dyn.strtab + (*this)->st_name,
365		    _dl_symcache[symidx].flags, flags, req_obj->load_name));
366#endif
367
368		_dl_symcache[symidx].sym = *this;
369		_dl_symcache[symidx].obj = sobj;
370		_dl_symcache[symidx].flags = flags;
371	}
372
373	return ret;
374}
375
376int _dl_searchnum = 0;
377void
378_dl_newsymsearch(void)
379{
380	_dl_searchnum += 1;
381
382	if (_dl_searchnum < 0) {
383		/*
384		 * If the signed number rolls over, reset all counters so
385		 * we dont get accidental collision.
386		 */
387		elf_object_t *walkobj;
388		for (walkobj = _dl_objects;
389		    walkobj != NULL;
390		    walkobj = walkobj->next) {
391			walkobj->lastlookup = 0;
392		}
393		_dl_searchnum = 1;
394	}
395}
396
397Elf_Addr
398_dl_find_symbol(const char *name, const Elf_Sym **this,
399    int flags, const Elf_Sym *ref_sym, elf_object_t *req_obj,
400    const elf_object_t **pobj)
401{
402	const Elf_Sym *weak_sym = NULL;
403	unsigned long h = 0;
404	const char *p = name;
405	elf_object_t *object = NULL, *weak_object = NULL;
406	int found = 0;
407	int visit = 0;
408	static int maxvisit = 0;
409	struct dep_node *n, *m;
410
411
412	while (*p) {
413		unsigned long g;
414		h = (h << 4) + *p++;
415		if ((g = h & 0xf0000000))
416			h ^= g >> 24;
417		h &= ~g;
418	}
419
420	if (req_obj->dyn.symbolic)
421		if (_dl_find_symbol_obj(req_obj, name, h, flags, this, &weak_sym,
422		    &weak_object)) {
423			object = req_obj;
424			found = 1;
425			goto found;
426		}
427
428	if (flags & SYM_SEARCH_OBJ) {
429		if (_dl_find_symbol_obj(req_obj, name, h, flags, this,
430		    &weak_sym, &weak_object)) {
431			object = req_obj;
432			found = 1;
433		}
434	} else if (flags & SYM_DLSYM) {
435		if (_dl_find_symbol_obj(req_obj, name, h, flags, this,
436		    &weak_sym, &weak_object)) {
437			object = req_obj;
438			found = 1;
439		}
440		if (weak_object != NULL && found == 0) {
441			object=weak_object;
442			*this = weak_sym;
443			found = 1;
444		}
445		/* search dlopened obj and all children */
446
447		if (found == 0) {
448			TAILQ_FOREACH(n, &req_obj->load_object->grpsym_list,
449			    next_sib) {
450				if (_dl_find_symbol_obj(n->data, name, h,
451				    flags, this,
452				    &weak_sym, &weak_object)) {
453					object = n->data;
454					found = 1;
455					break;
456				}
457			}
458		}
459	} else if ((flags & (SYM_SEARCH_NEXT|SYM_SEARCH_SELF|SYM_SEARCH_OTHER))) {
460		int skip = 0;
461
462		if ((flags & SYM_SEARCH_SELF) || (flags & SYM_SEARCH_NEXT))
463			skip = 1;
464
465		/*
466		 * search dlopened objects: global or req_obj == dlopened_obj
467		 * and and it's children
468		 */
469		TAILQ_FOREACH(n, &_dlopened_child_list, next_sib) {
470			if (((n->data->obj_flags & RTLD_GLOBAL) == 0) &&
471			    (n->data != req_obj->load_object))
472				continue;
473
474			TAILQ_FOREACH(m, &n->data->grpsym_list, next_sib) {
475				if (skip == 1) {
476					if (m->data == req_obj) {
477						skip = 0;
478						if (flags & SYM_SEARCH_NEXT)
479							continue;
480					} else
481						continue;
482				}
483				if ((flags & SYM_SEARCH_OTHER) &&
484				    (m->data == req_obj))
485					continue;
486				if (_dl_find_symbol_obj(m->data, name, h, flags,
487				    this, &weak_sym, &weak_object)) {
488					object = m->data;
489					found = 1;
490					goto found;
491				}
492			}
493		}
494	} else {
495		if (_dl_search_list_valid == 0) {
496			_dl_rebuild_allobj_grouplist();
497		}
498
499		TAILQ_FOREACH(n, &_dlsym_search_list, next_sib) {
500			if (n->data == req_obj->load_object) {
501				TAILQ_FOREACH(m, &n->data->grpsym_list,
502				    next_sib) {
503					visit++;
504					if (_dl_find_symbol_obj(m->data, name,
505					    h, flags, this, &weak_sym,
506					    &weak_object)) {
507						object = m->data;
508						found = 1;
509						goto found;
510					}
511				}
512			}
513			if (((n->data->obj_global & RTLD_GLOBAL) == 0) &&
514			    (n->data != req_obj->load_object))
515				continue;
516
517			//DL_DEB(("searching for %s in %s\n", name, n->data->load_name));
518			visit++;
519			if (_dl_find_symbol_obj(n->data, name, h, flags,
520			    this, &weak_sym, &weak_object)) {
521				object = n->data;
522				found = 1;
523				DL_DEB(("sym %s is in %s\n", name, object->load_name));
524				goto found;
525			}
526		}
527	}
528
529found:
530	if (visit > maxvisit) {
531		maxvisit = visit;
532		DL_DEB(("maxvisit is %d\n", maxvisit));
533	}
534	if (weak_object != NULL && found == 0) {
535		object=weak_object;
536		*this = weak_sym;
537		found = 1;
538	}
539
540
541	if (found == 0) {
542		if ((ref_sym == NULL ||
543		    (ELF_ST_BIND(ref_sym->st_info) != STB_WEAK)) &&
544		    (flags & SYM_WARNNOTFOUND))
545			_dl_printf("%s:%s: undefined symbol '%s'\n",
546			    _dl_progname, req_obj->load_name, name);
547		return (0);
548	}
549
550	if (ref_sym != NULL && ref_sym->st_size != 0 &&
551	    (ref_sym->st_size != (*this)->st_size)  &&
552	    (ELF_ST_TYPE((*this)->st_info) != STT_FUNC) ) {
553		_dl_printf("%s:%s: %s : WARNING: "
554		    "symbol(%s) size mismatch, relink your program\n",
555		    _dl_progname, req_obj->load_name,
556		    object->load_name, name);
557	}
558
559	if (pobj)
560		*pobj = object;
561
562	return (object->obj_base);
563}
564
565int
566_dl_find_symbol_obj(elf_object_t *object, const char *name, unsigned long hash,
567    int flags, const Elf_Sym **this, const Elf_Sym **weak_sym,
568    elf_object_t **weak_object)
569{
570	const Elf_Sym	*symt = object->dyn.symtab;
571	const char	*strt = object->dyn.strtab;
572	long	si;
573	const char *symn;
574
575	for (si = object->buckets[hash % object->nbuckets];
576	    si != STN_UNDEF; si = object->chains[si]) {
577		const Elf_Sym *sym = symt + si;
578
579		if (sym->st_value == 0)
580			continue;
581
582		if (ELF_ST_TYPE(sym->st_info) != STT_NOTYPE &&
583		    ELF_ST_TYPE(sym->st_info) != STT_OBJECT &&
584		    ELF_ST_TYPE(sym->st_info) != STT_FUNC)
585			continue;
586
587		symn = strt + sym->st_name;
588		if (sym != *this && _dl_strcmp(symn, name))
589			continue;
590
591		/* allow this symbol if we are referring to a function
592		 * which has a value, even if section is UNDEF.
593		 * this allows &func to refer to PLT as per the
594		 * ELF spec. st_value is checked above.
595		 * if flags has SYM_PLT set, we must have actual
596		 * symbol, so this symbol is skipped.
597		 */
598		if (sym->st_shndx == SHN_UNDEF) {
599			if ((flags & SYM_PLT) || sym->st_value == 0 ||
600			    ELF_ST_TYPE(sym->st_info) != STT_FUNC)
601				continue;
602		}
603
604		if (ELF_ST_BIND(sym->st_info) == STB_GLOBAL) {
605			*this = sym;
606			return 1;
607		} else if (ELF_ST_BIND(sym->st_info) == STB_WEAK) {
608			if (!*weak_sym) {
609				*weak_sym = sym;
610				*weak_object = object;
611			}
612		}
613	}
614	return 0;
615}
616
617void
618_dl_debug_state(void)
619{
620        /* Debugger stub */
621}
622