resolve.c revision 1.47 
1/*	$OpenBSD: resolve.c,v 1.47 2006/05/03 16:10:51 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, const long *dl_data,
74    const int objtype, const long laddr, const long loff)
75{
76	elf_object_t *object;
77#if 0
78	_dl_printf("objname [%s], dynp %p, dl_data %p, objtype %x laddr %lx, loff %lx\n",
79	    objname, dynp, dl_data, objtype, laddr, loff);
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] += loff;
107	if (object->Dyn.info[DT_HASH])
108		object->Dyn.info[DT_HASH] += loff;
109	if (object->Dyn.info[DT_STRTAB])
110		object->Dyn.info[DT_STRTAB] += loff;
111	if (object->Dyn.info[DT_SYMTAB])
112		object->Dyn.info[DT_SYMTAB] += loff;
113	if (object->Dyn.info[DT_RELA])
114		object->Dyn.info[DT_RELA] += loff;
115	if (object->Dyn.info[DT_SONAME])
116		object->Dyn.info[DT_SONAME] += loff;
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] += loff;
121	if (object->Dyn.info[DT_INIT])
122		object->Dyn.info[DT_INIT] += loff;
123	if (object->Dyn.info[DT_FINI])
124		object->Dyn.info[DT_FINI] += loff;
125	if (object->Dyn.info[DT_JMPREL])
126		object->Dyn.info[DT_JMPREL] += loff;
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	if (dl_data) {
138		object->phdrp = (Elf_Phdr *) dl_data[AUX_phdr];
139		object->phdrc = dl_data[AUX_phnum];
140	}
141	object->obj_type = objtype;
142	object->load_addr = laddr;
143	object->load_offs = loff;
144	object->load_name = _dl_strdup(objname);
145	if (_dl_loading_object == NULL) {
146		/*
147		 * no loading object, object is the loading object,
148		 * as it is either executable, or dlopened()
149		 */
150		_dl_loading_object = object->load_object = object;
151		DL_DEB(("head %s\n", object->load_name ));
152	} else {
153		object->load_object = _dl_loading_object;
154	}
155	DL_DEB(("obj %s has %s as head\n", object->load_name,
156	    _dl_loading_object->load_name ));
157	object->refcount = 0;
158	TAILQ_INIT(&object->child_list);
159	object->opencount = 0;	/* # dlopen() & exe */
160	object->grprefcount = 0;
161	/* default dev, inode for dlopen-able objects. */
162	object->dev = 0;
163	object->inode = 0;
164	TAILQ_INIT(&object->grpsym_list);
165	TAILQ_INIT(&object->grpref_list);
166
167	return(object);
168}
169
170void
171_dl_tailq_free(struct dep_node *n)
172{
173	struct dep_node *next;
174
175	while (n != NULL) {
176		next = TAILQ_NEXT(n, next_sib);
177		_dl_free(n);
178		n = next;
179	}
180}
181
182elf_object_t *free_objects;
183
184void _dl_cleanup_objects(void);
185void
186_dl_cleanup_objects()
187{
188	elf_object_t *nobj, *head;
189	struct dep_node *n, *next;
190
191	n = TAILQ_FIRST(&_dlopened_child_list);
192	while (n != NULL) {
193		next = TAILQ_NEXT(n, next_sib);
194		if (OBJECT_DLREF_CNT(n->data) == 0) {
195			TAILQ_REMOVE(&_dlopened_child_list, n, next_sib);
196			_dl_free(n);
197		}
198		n = next;
199	}
200
201	head = free_objects;
202	free_objects = NULL;
203	while (head != NULL) {
204		if (head->load_name)
205			_dl_free(head->load_name);
206		_dl_tailq_free(TAILQ_FIRST(&head->grpsym_list));
207		_dl_tailq_free(TAILQ_FIRST(&head->child_list));
208		_dl_tailq_free(TAILQ_FIRST(&head->grpref_list));
209		nobj = head->next;
210		_dl_free(head);
211		head = nobj;
212	}
213}
214
215void
216_dl_remove_object(elf_object_t *object)
217{
218	object->prev->next = object->next;
219	if (object->next)
220		object->next->prev = object->prev;
221
222	if (_dl_last_object == object)
223		_dl_last_object = object->prev;
224
225	object->next = free_objects;
226	free_objects = object;
227}
228
229
230elf_object_t *
231_dl_lookup_object(const char *name)
232{
233	elf_object_t *object;
234
235	object = _dl_objects;
236	while (object) {
237		if (_dl_strcmp(name, object->load_name) == 0)
238			return(object);
239		object = object->next;
240	}
241	return(0);
242}
243
244int _dl_find_symbol_obj(elf_object_t *object, const char *name,
245    unsigned long hash, int flags, const Elf_Sym **ref,
246    const Elf_Sym **weak_sym,
247    elf_object_t **weak_object);
248
249sym_cache *_dl_symcache;
250int _dl_symcachestat_hits;
251int _dl_symcachestat_lookups;
252
253
254Elf_Addr
255_dl_find_symbol_bysym(elf_object_t *req_obj, unsigned int symidx,
256    const Elf_Sym **this, int flags, const Elf_Sym *ref_sym, const elf_object_t **pobj)
257{
258	Elf_Addr ret;
259	const Elf_Sym *sym;
260	const char *symn;
261	const elf_object_t *sobj;
262
263	_dl_symcachestat_lookups ++;
264	if (_dl_symcache != NULL &&
265	    symidx < req_obj->nchains &&
266	    _dl_symcache[symidx].obj != NULL &&
267	    _dl_symcache[symidx].sym != NULL &&
268	    _dl_symcache[symidx].flags == flags) {
269
270		_dl_symcachestat_hits++;
271		sobj = _dl_symcache[symidx].obj;
272		*this = _dl_symcache[symidx].sym;
273		if (pobj)
274			*pobj = sobj;
275		if (_dl_prebind_validate) /* XXX */
276			prebind_validate(req_obj, symidx, flags, ref_sym);
277		return sobj->load_offs;
278	}
279
280	sym = req_obj->dyn.symtab;
281	sym += symidx;
282	symn = req_obj->dyn.strtab + sym->st_name;
283
284	ret = _dl_find_symbol(symn, this, flags, ref_sym, req_obj, &sobj);
285
286	if (pobj)
287		*pobj = sobj;
288
289	if (_dl_symcache != NULL && symidx < req_obj->nchains) {
290#if 0
291		DL_DEB(("cache miss %d %p %p, %p %p %s %s %d %d %s\n",
292		    symidx,
293		    _dl_symcache[symidx].sym, *this,
294		    _dl_symcache[symidx].obj, sobj, sobj->load_name,
295		    sobj->dyn.strtab + (*this)->st_name,
296		    _dl_symcache[symidx].flags, flags, req_obj->load_name));
297#endif
298
299		_dl_symcache[symidx].sym = *this;
300		_dl_symcache[symidx].obj = sobj;
301		_dl_symcache[symidx].flags = flags;
302	}
303
304	return ret;
305}
306
307Elf_Addr
308_dl_find_symbol(const char *name, const Elf_Sym **this,
309    int flags, const Elf_Sym *ref_sym, elf_object_t *req_obj,
310    const elf_object_t **pobj)
311{
312	const Elf_Sym *weak_sym = NULL;
313	unsigned long h = 0;
314	const char *p = name;
315	elf_object_t *object = NULL, *weak_object = NULL;
316	int found = 0;
317	struct dep_node *n, *m;
318
319
320	while (*p) {
321		unsigned long g;
322		h = (h << 4) + *p++;
323		if ((g = h & 0xf0000000))
324			h ^= g >> 24;
325		h &= ~g;
326	}
327
328	if (req_obj->dyn.symbolic)
329		if (_dl_find_symbol_obj(req_obj, name, h, flags, this, &weak_sym,
330		    &weak_object)) {
331			object = req_obj;
332			found = 1;
333			goto found;
334		}
335
336	if (flags & SYM_SEARCH_OBJ) {
337		if (_dl_find_symbol_obj(req_obj, name, h, flags, this,
338		    &weak_sym, &weak_object)) {
339			object = req_obj;
340			found = 1;
341		}
342	} else if (flags & SYM_DLSYM) {
343		if (_dl_find_symbol_obj(req_obj, name, h, flags, this,
344		    &weak_sym, &weak_object)) {
345			object = req_obj;
346			found = 1;
347		}
348		if (weak_object != NULL && found == 0) {
349			object=weak_object;
350			*this = weak_sym;
351			found = 1;
352		}
353		/* search dlopened obj and all children */
354
355		if (found == 0) {
356			TAILQ_FOREACH(n, &req_obj->load_object->grpsym_list,
357			    next_sib) {
358				if (_dl_find_symbol_obj(n->data, name, h,
359				    flags, this,
360				    &weak_sym, &weak_object)) {
361					object = n->data;
362					found = 1;
363					break;
364				}
365			}
366		}
367	} else {
368		int skip = 0;
369
370		if ((flags & SYM_SEARCH_SELF) || (flags & SYM_SEARCH_NEXT))
371			skip = 1;
372
373		/*
374		 * search dlopened objects: global or req_obj == dlopened_obj
375		 * and and it's children
376		 */
377		TAILQ_FOREACH(n, &_dlopened_child_list, next_sib) {
378			if (((n->data->obj_flags & RTLD_GLOBAL) == 0) &&
379			    (n->data != req_obj->load_object))
380				continue;
381
382			TAILQ_FOREACH(m, &n->data->grpsym_list, next_sib) {
383				if (skip == 1) {
384					if (m->data == req_obj) {
385						skip = 0;
386						if (flags & SYM_SEARCH_NEXT)
387							continue;
388					} else
389						continue;
390				}
391				if ((flags & SYM_SEARCH_OTHER) &&
392				    (m->data == req_obj))
393					continue;
394				if (_dl_find_symbol_obj(m->data, name, h, flags,
395				    this, &weak_sym, &weak_object)) {
396					object = m->data;
397					found = 1;
398					goto found;
399				}
400			}
401		}
402	}
403
404found:
405	if (weak_object != NULL && found == 0) {
406		object=weak_object;
407		*this = weak_sym;
408		found = 1;
409	}
410
411
412	if (found == 0) {
413		if ((ref_sym == NULL ||
414		    (ELF_ST_BIND(ref_sym->st_info) != STB_WEAK)) &&
415		    (flags & SYM_WARNNOTFOUND))
416			_dl_printf("%s:%s: undefined symbol '%s'\n",
417			    _dl_progname, req_obj->load_name, name);
418		return (0);
419	}
420
421	if (ref_sym != NULL && ref_sym->st_size != 0 &&
422	    (ref_sym->st_size != (*this)->st_size)  &&
423	    (ELF_ST_TYPE((*this)->st_info) != STT_FUNC) ) {
424		_dl_printf("%s:%s: %s : WARNING: "
425		    "symbol(%s) size mismatch, relink your program\n",
426		    _dl_progname, req_obj->load_name,
427		    object->load_name, name);
428	}
429
430	if (pobj)
431		*pobj = object;
432
433	return (object->load_offs);
434}
435
436int
437_dl_find_symbol_obj(elf_object_t *object, const char *name, unsigned long hash,
438    int flags, const Elf_Sym **this, const Elf_Sym **weak_sym,
439    elf_object_t **weak_object)
440{
441	const Elf_Sym	*symt = object->dyn.symtab;
442	const char	*strt = object->dyn.strtab;
443	long	si;
444	const char *symn;
445
446	for (si = object->buckets[hash % object->nbuckets];
447	    si != STN_UNDEF; si = object->chains[si]) {
448		const Elf_Sym *sym = symt + si;
449
450		if (sym->st_value == 0)
451			continue;
452
453		if (ELF_ST_TYPE(sym->st_info) != STT_NOTYPE &&
454		    ELF_ST_TYPE(sym->st_info) != STT_OBJECT &&
455		    ELF_ST_TYPE(sym->st_info) != STT_FUNC)
456			continue;
457
458		symn = strt + sym->st_name;
459		if (sym != *this && _dl_strcmp(symn, name))
460			continue;
461
462		/* allow this symbol if we are referring to a function
463		 * which has a value, even if section is UNDEF.
464		 * this allows &func to refer to PLT as per the
465		 * ELF spec. st_value is checked above.
466		 * if flags has SYM_PLT set, we must have actual
467		 * symbol, so this symbol is skipped.
468		 */
469		if (sym->st_shndx == SHN_UNDEF) {
470			if ((flags & SYM_PLT) || sym->st_value == 0 ||
471			    ELF_ST_TYPE(sym->st_info) != STT_FUNC)
472				continue;
473		}
474
475		if (ELF_ST_BIND(sym->st_info) == STB_GLOBAL) {
476			*this = sym;
477			return 1;
478		} else if (ELF_ST_BIND(sym->st_info) == STB_WEAK) {
479			if (!*weak_sym) {
480				*weak_sym = sym;
481				*weak_object = object;
482			}
483		}
484	}
485	return 0;
486}
487