resolve.c revision 1.50 
1/*	$OpenBSD: resolve.c,v 1.50 2010/07/01 19:25:44 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] += obase;
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		_dl_tailq_free(TAILQ_FIRST(&head->grpsym_list));
206		_dl_tailq_free(TAILQ_FIRST(&head->child_list));
207		_dl_tailq_free(TAILQ_FIRST(&head->grpref_list));
208		nobj = head->next;
209		_dl_free(head);
210		head = nobj;
211	}
212}
213
214void
215_dl_remove_object(elf_object_t *object)
216{
217	object->prev->next = object->next;
218	if (object->next)
219		object->next->prev = object->prev;
220
221	if (_dl_last_object == object)
222		_dl_last_object = object->prev;
223
224	object->next = free_objects;
225	free_objects = object;
226}
227
228
229elf_object_t *
230_dl_lookup_object(const char *name)
231{
232	elf_object_t *object;
233
234	object = _dl_objects;
235	while (object) {
236		if (_dl_strcmp(name, object->load_name) == 0)
237			return(object);
238		object = object->next;
239	}
240	return(0);
241}
242
243int _dl_find_symbol_obj(elf_object_t *object, const char *name,
244    unsigned long hash, int flags, const Elf_Sym **ref,
245    const Elf_Sym **weak_sym,
246    elf_object_t **weak_object);
247
248sym_cache *_dl_symcache;
249int _dl_symcachestat_hits;
250int _dl_symcachestat_lookups;
251
252
253Elf_Addr
254_dl_find_symbol_bysym(elf_object_t *req_obj, unsigned int symidx,
255    const Elf_Sym **this, int flags, const Elf_Sym *ref_sym, const elf_object_t **pobj)
256{
257	Elf_Addr ret;
258	const Elf_Sym *sym;
259	const char *symn;
260	const elf_object_t *sobj;
261
262	_dl_symcachestat_lookups ++;
263	if (_dl_symcache != NULL &&
264	    symidx < req_obj->nchains &&
265	    _dl_symcache[symidx].obj != NULL &&
266	    _dl_symcache[symidx].sym != NULL &&
267	    _dl_symcache[symidx].flags == flags) {
268
269		_dl_symcachestat_hits++;
270		sobj = _dl_symcache[symidx].obj;
271		*this = _dl_symcache[symidx].sym;
272		if (pobj)
273			*pobj = sobj;
274		if (_dl_prebind_validate) /* XXX */
275			prebind_validate(req_obj, symidx, flags, ref_sym);
276		return sobj->obj_base;
277	}
278
279	sym = req_obj->dyn.symtab;
280	sym += symidx;
281	symn = req_obj->dyn.strtab + sym->st_name;
282
283	ret = _dl_find_symbol(symn, this, flags, ref_sym, req_obj, &sobj);
284
285	if (pobj)
286		*pobj = sobj;
287
288	if (_dl_symcache != NULL && symidx < req_obj->nchains) {
289#if 0
290		DL_DEB(("cache miss %d %p %p, %p %p %s %s %d %d %s\n",
291		    symidx,
292		    _dl_symcache[symidx].sym, *this,
293		    _dl_symcache[symidx].obj, sobj, sobj->load_name,
294		    sobj->dyn.strtab + (*this)->st_name,
295		    _dl_symcache[symidx].flags, flags, req_obj->load_name));
296#endif
297
298		_dl_symcache[symidx].sym = *this;
299		_dl_symcache[symidx].obj = sobj;
300		_dl_symcache[symidx].flags = flags;
301	}
302
303	return ret;
304}
305
306uint32_t _dl_searchnum = 0;
307void
308_dl_newsymsearch(void)
309{
310	_dl_searchnum += 1;
311
312	if (_dl_searchnum < 0) {
313		/* if the signed number roll over, reset
314		 * all counters so we dont get accidental collision
315		 */
316		elf_object_t *walkobj;
317		for (walkobj = _dl_objects;
318		    walkobj != NULL;
319		    walkobj = walkobj->next) {
320			walkobj->lastlookup = 0;
321		}
322		_dl_searchnum = 1;
323	}
324}
325
326Elf_Addr
327_dl_find_symbol(const char *name, const Elf_Sym **this,
328    int flags, const Elf_Sym *ref_sym, elf_object_t *req_obj,
329    const elf_object_t **pobj)
330{
331	const Elf_Sym *weak_sym = NULL;
332	unsigned long h = 0;
333	const char *p = name;
334	elf_object_t *object = NULL, *weak_object = NULL;
335	int found = 0;
336	struct dep_node *n, *m;
337
338
339	while (*p) {
340		unsigned long g;
341		h = (h << 4) + *p++;
342		if ((g = h & 0xf0000000))
343			h ^= g >> 24;
344		h &= ~g;
345	}
346
347	if (req_obj->dyn.symbolic)
348		if (_dl_find_symbol_obj(req_obj, name, h, flags, this, &weak_sym,
349		    &weak_object)) {
350			object = req_obj;
351			found = 1;
352			goto found;
353		}
354
355	if (flags & SYM_SEARCH_OBJ) {
356		if (_dl_find_symbol_obj(req_obj, name, h, flags, this,
357		    &weak_sym, &weak_object)) {
358			object = req_obj;
359			found = 1;
360		}
361	} else if (flags & SYM_DLSYM) {
362		if (_dl_find_symbol_obj(req_obj, name, h, flags, this,
363		    &weak_sym, &weak_object)) {
364			object = req_obj;
365			found = 1;
366		}
367		if (weak_object != NULL && found == 0) {
368			object=weak_object;
369			*this = weak_sym;
370			found = 1;
371		}
372		/* search dlopened obj and all children */
373
374		if (found == 0) {
375			TAILQ_FOREACH(n, &req_obj->load_object->grpsym_list,
376			    next_sib) {
377				if (_dl_find_symbol_obj(n->data, name, h,
378				    flags, this,
379				    &weak_sym, &weak_object)) {
380					object = n->data;
381					found = 1;
382					break;
383				}
384			}
385		}
386	} else {
387		int skip = 0;
388
389		if ((flags & SYM_SEARCH_SELF) || (flags & SYM_SEARCH_NEXT))
390			skip = 1;
391
392		_dl_newsymsearch();
393
394		/*
395		 * search dlopened objects: global or req_obj == dlopened_obj
396		 * and and it's children
397		 */
398		TAILQ_FOREACH(n, &_dlopened_child_list, next_sib) {
399			if (((n->data->obj_flags & RTLD_GLOBAL) == 0) &&
400			    (n->data != req_obj->load_object))
401				continue;
402
403			n->data->lastlookup_head = _dl_searchnum;
404			TAILQ_FOREACH(m, &n->data->grpsym_list, next_sib) {
405				if (skip == 1) {
406					if (m->data == req_obj) {
407						skip = 0;
408						if (flags & SYM_SEARCH_NEXT)
409							continue;
410					} else
411						continue;
412				}
413				if ((flags & SYM_SEARCH_OTHER) &&
414				    (m->data == req_obj))
415					continue;
416				m->data->lastlookup = _dl_searchnum;
417				if (_dl_find_symbol_obj(m->data, name, h, flags,
418				    this, &weak_sym, &weak_object)) {
419					object = m->data;
420					found = 1;
421					goto found;
422				}
423			}
424		}
425	}
426
427found:
428	if (weak_object != NULL && found == 0) {
429		object=weak_object;
430		*this = weak_sym;
431		found = 1;
432	}
433
434
435	if (found == 0) {
436		if ((ref_sym == NULL ||
437		    (ELF_ST_BIND(ref_sym->st_info) != STB_WEAK)) &&
438		    (flags & SYM_WARNNOTFOUND))
439			_dl_printf("%s:%s: undefined symbol '%s'\n",
440			    _dl_progname, req_obj->load_name, name);
441		return (0);
442	}
443
444	if (ref_sym != NULL && ref_sym->st_size != 0 &&
445	    (ref_sym->st_size != (*this)->st_size)  &&
446	    (ELF_ST_TYPE((*this)->st_info) != STT_FUNC) ) {
447		_dl_printf("%s:%s: %s : WARNING: "
448		    "symbol(%s) size mismatch, relink your program\n",
449		    _dl_progname, req_obj->load_name,
450		    object->load_name, name);
451	}
452
453	if (pobj)
454		*pobj = object;
455
456	return (object->obj_base);
457}
458
459int
460_dl_find_symbol_obj(elf_object_t *object, const char *name, unsigned long hash,
461    int flags, const Elf_Sym **this, const Elf_Sym **weak_sym,
462    elf_object_t **weak_object)
463{
464	const Elf_Sym	*symt = object->dyn.symtab;
465	const char	*strt = object->dyn.strtab;
466	long	si;
467	const char *symn;
468
469	for (si = object->buckets[hash % object->nbuckets];
470	    si != STN_UNDEF; si = object->chains[si]) {
471		const Elf_Sym *sym = symt + si;
472
473		if (sym->st_value == 0)
474			continue;
475
476		if (ELF_ST_TYPE(sym->st_info) != STT_NOTYPE &&
477		    ELF_ST_TYPE(sym->st_info) != STT_OBJECT &&
478		    ELF_ST_TYPE(sym->st_info) != STT_FUNC)
479			continue;
480
481		symn = strt + sym->st_name;
482		if (sym != *this && _dl_strcmp(symn, name))
483			continue;
484
485		/* allow this symbol if we are referring to a function
486		 * which has a value, even if section is UNDEF.
487		 * this allows &func to refer to PLT as per the
488		 * ELF spec. st_value is checked above.
489		 * if flags has SYM_PLT set, we must have actual
490		 * symbol, so this symbol is skipped.
491		 */
492		if (sym->st_shndx == SHN_UNDEF) {
493			if ((flags & SYM_PLT) || sym->st_value == 0 ||
494			    ELF_ST_TYPE(sym->st_info) != STT_FUNC)
495				continue;
496		}
497
498		if (ELF_ST_BIND(sym->st_info) == STB_GLOBAL) {
499			*this = sym;
500			return 1;
501		} else if (ELF_ST_BIND(sym->st_info) == STB_WEAK) {
502			if (!*weak_sym) {
503				*weak_sym = sym;
504				*weak_object = object;
505			}
506		}
507	}
508	return 0;
509}
510